feat(dc/tool-c): Add pivot column ordering and NA handling features

Major features:
1. Pivot transformation enhancements:
   - Add option to keep unselected columns with 3 aggregation methods
   - Maintain original column order after pivot (aligned with source file)
   - Preserve pivot value order (first appearance order)

2. NA handling across 4 core functions:
   - Recode: Support keep/map/drop for NA values
   - Filter: Already supports is_null/not_null operators
   - Binning: Support keep/label/assign for NA values (fix nan display)
   - Conditional: Add is_null/not_null operators

3. UI improvements:
   - Enable column header tooltips with custom header component
   - Add closeable alert for 50-row preview
   - Fix page scrollbar issues

Modified files:
Python: pivot.py, recode.py, binning.py, conditional.py, main.py
Backend: SessionController, QuickActionController, QuickActionService
Frontend: PivotDialog, RecodeDialog, BinningDialog, ConditionalDialog, DataGrid, index

Status: Ready for testing

frontend-v2/src/modules/dc/pages/tool-c/components/BinningDialog.tsx

@@ -42,6 +42,11 @@ const BinningDialog: React.FC<BinningDialogProps> = ({
   const [autoLabels, setAutoLabels] = useState<string[]>(['低', '中', '高']);
   
   const [loading, setLoading] = useState(false);
+  
+  // ✨ NA处理
+  const [naHandling, setNaHandling] = useState<'keep' | 'label' | 'assign'>('keep');
+  const [naLabel, setNaLabel] = useState<string>('缺失');
+  const [naAssignTo, setNaAssignTo] = useState<number>(0);
 
   // 更新列选择
   const handleColumnChange = (value: string) => {
@@ -118,6 +123,14 @@ const BinningDialog: React.FC<BinningDialogProps> = ({
       }
     }
 
+    // ✨ 添加NA处理参数
+    params.naHandling = naHandling;
+    if (naHandling === 'label') {
+      params.naLabel = naLabel;
+    } else if (naHandling === 'assign') {
+      params.naAssignTo = naAssignTo;
+    }
+
     setLoading(true);
     try {
       const response = await fetch('/api/v1/dc/tool-c/quick-action', {
@@ -328,6 +341,59 @@ const BinningDialog: React.FC<BinningDialogProps> = ({
                 onChange={(e) => setNewColumnName(e.target.value)}
               />
             </div>
+
+            {/* ✨ NA处理区域 */}
+            <div className="bg-yellow-50 p-4 rounded-lg border border-yellow-200">
+              <div className="flex items-center gap-2 mb-3">
+                <span className="text-sm font-medium text-slate-700">⚠️ 空值/NA 处理</span>
+                <span className="text-xs text-slate-500">（原列中的空值如何处理）</span>
+              </div>
+              
+              <Radio.Group value={naHandling} onChange={(e) => setNaHandling(e.target.value)}>
+                <Space direction="vertical">
+                  <Radio value="keep">
+                    <span className="text-sm">保持为空（默认）</span>
+                  </Radio>
+                  <Radio value="label">
+                    <span className="text-sm">标记为指定标签</span>
+                    {naHandling === 'label' && (
+                      <Input
+                        placeholder="如：缺失、未知"
+                        value={naLabel}
+                        onChange={(e) => setNaLabel(e.target.value)}
+                        size="small"
+                        className="ml-2"
+                        style={{ width: 150 }}
+                      />
+                    )}
+                  </Radio>
+                  <Radio value="assign">
+                    <span className="text-sm">分配到指定组</span>
+                    {naHandling === 'assign' && (
+                      <Select
+                        value={naAssignTo}
+                        onChange={setNaAssignTo}
+                        size="small"
+                        className="ml-2"
+                        style={{ width: 150 }}
+                      >
+                        {(method === 'custom' 
+                          ? (customLabels.split(',').filter(l => l.trim()).length || 3)
+                          : numBins
+                        ) && Array.from({ length: method === 'custom' 
+                          ? (customLabels.split(',').filter(l => l.trim()).length || 3)
+                          : numBins
+                        }).map((_, i) => (
+                          <Select.Option key={i} value={i}>
+                            第 {i + 1} 组
+                          </Select.Option>
+                        ))}
+                      </Select>
+                    )}
+                  </Radio>
+                </Space>
+              </Radio.Group>
+            </div>
           </>
         )}
 

frontend-v2/src/modules/dc/pages/tool-c/components/ConditionalDialog.tsx

@@ -51,6 +51,8 @@ const ConditionalDialog: React.FC<Props> = ({
     { label: '小于 (<)', value: '<' },
     { label: '大于等于 (>=)', value: '>=' },
     { label: '小于等于 (<=)', value: '<=' },
+    { label: '为空（空值/NA）', value: 'is_null' },  // ✨ 新增
+    { label: '不为空', value: 'not_null' },  // ✨ 新增
   ];
 
   // 添加规则
@@ -365,20 +367,23 @@ const ConditionalDialog: React.FC<Props> = ({
                             </Select.Option>
                           ))}
                         </Select>
-                        <Input
-                          placeholder="值"
-                          value={condition.value}
-                          onChange={(e) =>
-                            handleUpdateCondition(
-                              ruleIndex,
-                              condIndex,
-                              'value',
-                              e.target.value
-                            )
-                          }
-                          className="w-32"
-                          size="small"
-                        />
+                        {/* ✨ 只在不是is_null/not_null时显示值输入框 */}
+                        {condition.operator !== 'is_null' && condition.operator !== 'not_null' && (
+                          <Input
+                            placeholder="值"
+                            value={condition.value}
+                            onChange={(e) =>
+                              handleUpdateCondition(
+                                ruleIndex,
+                                condIndex,
+                                'value',
+                                e.target.value
+                              )
+                            }
+                            className="w-32"
+                            size="small"
+                          />
+                        )}
                         {rule.conditions.length > 1 && (
                           <Button
                             type="text"

frontend-v2/src/modules/dc/pages/tool-c/components/DataGrid.tsx

@@ -23,6 +23,19 @@ interface DataGridProps {
   onCellValueChanged?: (params: any) => void;
 }
 
+// ✨ 自定义表头组件（带tooltip）
+const CustomHeader = (props: any) => {
+  return (
+    <div 
+      className="ag-header-cell-label" 
+      title={props.displayName}
+      style={{ overflow: 'hidden', textOverflow: 'ellipsis', whiteSpace: 'nowrap' }}
+    >
+      {props.displayName}
+    </div>
+  );
+};
+
 const DataGrid: React.FC<DataGridProps> = ({ data, columns, onCellValueChanged }) => {
   // 防御性编程：确保 data 和 columns 始终是数组
   const safeData = data || [];
@@ -41,8 +54,13 @@ const DataGrid: React.FC<DataGridProps> = ({ data, columns, onCellValueChanged }
         // ✅ 修复：使用安全的field名（索引），通过valueGetter获取实际数据
         field: `col_${index}`,
         headerName: col.name,
-        // ✅ 优化：添加tooltip显示完整列名
+        // ✅ 优化：添加tooltip显示完整列名（双保险）
         headerTooltip: col.name,
+        // ✨ 使用自定义表头组件（确保tooltip一定显示）
+        headerComponent: CustomHeader,
+        headerComponentParams: {
+          displayName: col.name,
+        },
         // ✅ 关键修复：使用valueGetter直接从原始数据中获取值
         valueGetter: (params: any) => {
           return params.data?.[col.id];
@@ -93,7 +111,7 @@ const DataGrid: React.FC<DataGridProps> = ({ data, columns, onCellValueChanged }
   // 空状态
   if (safeData.length === 0) {
     return (
-      <div className="bg-white border-2 border-slate-200 shadow-lg rounded-2xl p-12 text-center h-full flex items-center justify-center">
+      <div className="bg-white border-2 border-slate-200 shadow-lg rounded-2xl p-12 text-center flex items-center justify-center" style={{ height: '100%' }}>
         <div className="text-slate-400 text-sm space-y-3">
           <p className="text-2xl">📊 暂无数据</p>
           <p className="text-base text-slate-500">请在右侧AI助手中上传CSV或Excel文件</p>
@@ -118,6 +136,8 @@ const DataGrid: React.FC<DataGridProps> = ({ data, columns, onCellValueChanged }
           domLayout="normal"
           suppressCellFocus={false}
           enableCellTextSelection={true}
+          // ✅ 启用浏览器原生tooltip（让headerTooltip生效）
+          enableBrowserTooltips={true}
           // ✅ 修复 AG Grid #239：使用 legacy 主题模式
           theme="legacy"
           // 性能优化

frontend-v2/src/modules/dc/pages/tool-c/components/PivotDialog.tsx

@@ -23,6 +23,9 @@ const PivotDialog: React.FC<Props> = ({
   const [valueColumns, setValueColumns] = useState<string[]>([]);
   const [aggfunc, setAggfunc] = useState<'first' | 'last' | 'mean' | 'sum'>('first');
   const [loading, setLoading] = useState(false);
+  // ✨ 新增：未选择列的处理
+  const [keepUnusedColumns, setKeepUnusedColumns] = useState(false);
+  const [unusedAggMethod, setUnusedAggMethod] = useState<'first' | 'mode' | 'mean'>('first');
   
   // 重置状态
   useEffect(() => {
@@ -31,6 +34,8 @@ const PivotDialog: React.FC<Props> = ({
       setPivotColumn('');
       setValueColumns([]);
       setAggfunc('first');
+      setKeepUnusedColumns(false);  // ✨ 重置：不保留未选择的列
+      setUnusedAggMethod('first');  // ✨ 重置：默认取第一个值
     }
   }, [visible]);
   
@@ -71,6 +76,8 @@ const PivotDialog: React.FC<Props> = ({
             pivotColumn,
             valueColumns,
             aggfunc,
+            keepUnusedColumns,  // ✨ 新增：是否保留未选择的列
+            unusedAggMethod,  // ✨ 新增：未选择列的聚合方式
           },
         }),
       });
@@ -238,6 +245,53 @@ const PivotDialog: React.FC<Props> = ({
           </div>
         </div>
         
+        {/* ✨ 高级选项 */}
+        <div className="border-t pt-4">
+          <div className="flex items-center gap-2 mb-3">
+            <span className="text-sm font-medium text-slate-700">⚙️ 高级选项</span>
+          </div>
+          
+          <Checkbox
+            checked={keepUnusedColumns}
+            onChange={(e) => setKeepUnusedColumns(e.target.checked)}
+          >
+            <span className="text-sm font-medium">保留未选择的列</span>
+          </Checkbox>
+          
+          {keepUnusedColumns && (
+            <div className="ml-6 mt-3 p-3 bg-slate-50 rounded-lg border border-slate-200">
+              <label className="text-sm font-medium text-slate-700 mb-2 block">
+                聚合方式：
+              </label>
+              <Radio.Group
+                value={unusedAggMethod}
+                onChange={(e) => setUnusedAggMethod(e.target.value)}
+              >
+                <div className="space-y-2">
+                  <Radio value="first">
+                    <div className="ml-2">
+                      <span className="font-medium text-sm">取第一个值</span>
+                      <span className="text-xs text-slate-500 ml-2">（默认）</span>
+                    </div>
+                  </Radio>
+                  <Radio value="mode">
+                    <span className="ml-2 font-medium text-sm">取众数</span>
+                  </Radio>
+                  <Radio value="mean">
+                    <div className="ml-2">
+                      <span className="font-medium text-sm">取均值</span>
+                      <span className="text-xs text-slate-500 ml-2">（仅数值列）</span>
+                    </div>
+                  </Radio>
+                </div>
+              </Radio.Group>
+              <div className="text-xs text-slate-500 mt-2">
+                未选择的列将按此方式聚合，并保留在结果中
+              </div>
+            </div>
+          )}
+        </div>
+        
         {/* 警告 */}
         <Alert
           title="重要提示"

frontend-v2/src/modules/dc/pages/tool-c/components/RecodeDialog.tsx

@@ -40,6 +40,11 @@ const RecodeDialog: React.FC<RecodeDialogProps> = ({
   const [newColumnName, setNewColumnName] = useState('');
   const [loading, setLoading] = useState(false);
   const [extracting, setExtracting] = useState(false);
+  // ✨ NA处理
+  const [hasNA, setHasNA] = useState(false);
+  const [naCount, setNaCount] = useState(0);  // ✨ NA数量
+  const [naHandling, setNaHandling] = useState<'keep' | 'map' | 'drop'>('keep');
+  const [naValue, setNaValue] = useState<string>('');
 
   // 当选择列时，从后端获取唯一值
   useEffect(() => {
@@ -65,17 +70,38 @@ const RecodeDialog: React.FC<RecodeDialogProps> = ({
         }
         
         const unique = result.data.uniqueValues;
+        const naCountFromBackend = result.data.naCount || 0;  // ✨ 从后端获取NA数量
         
         setUniqueValues(unique);
         
-        // 初始化映射表
-        const initialMapping = unique.map((val: any) => ({
+        // ✨ 检测是否有NA值（后端用<空值/NA>标记）
+        const hasNAValue = unique.some((val: any) => 
+          val === null || 
+          val === undefined || 
+          val === '' || 
+          val === '<空值/NA>'  // ✨ 后端返回的特殊标记
+        );
+        setHasNA(hasNAValue);
+        setNaCount(naCountFromBackend);  // ✨ 保存NA数量
+        
+        // 初始化映射表（排除NA值，NA单独处理）
+        const nonNAValues = unique.filter((val: any) => 
+          val !== null && 
+          val !== undefined && 
+          val !== '' && 
+          val !== '<空值/NA>'  // ✨ 排除特殊标记
+        );
+        const initialMapping = nonNAValues.map((val: any) => ({
           originalValue: val,
           newValue: '',
         }));
         
         setMappingTable(initialMapping);
         
+        // 重置NA处理
+        setNaHandling('keep');
+        setNaValue('');
+        
         // 生成默认新列名
         setNewColumnName(`${selectedColumn}_编码`);
       } catch (error: any) {
@@ -172,6 +198,8 @@ const RecodeDialog: React.FC<RecodeDialogProps> = ({
             mapping,
             createNewColumn,
             newColumnName: createNewColumn ? newColumnName : undefined,
+            naHandling,  // ✨ NA处理方式
+            naValue: naHandling === 'map' ? naValue : undefined,  // ✨ NA映射值
           },
         }),
       });
@@ -239,7 +267,12 @@ const RecodeDialog: React.FC<RecodeDialogProps> = ({
                 <div>
                   <div className="flex items-center justify-between mb-2">
                     <label className="text-sm font-medium text-slate-700">
-                      检测到 {uniqueValues.length} 个唯一值：
+                      检测到 {mappingTable.length} 个唯一值：
+                      {hasNA && (
+                        <span className="ml-2 text-xs text-yellow-600">
+                          （+空值/NA，见下方处理）
+                        </span>
+                      )}
                     </label>
                     <span className="text-xs text-slate-500">
                       💡 提示：可以批量设置（如：1,2,3...）
@@ -276,6 +309,46 @@ const RecodeDialog: React.FC<RecodeDialogProps> = ({
                     </div>
                   )}
                 </div>
+
+                {/* ✨ NA处理区域 */}
+                {hasNA && (
+                  <div className="bg-yellow-50 p-3 rounded-lg border border-yellow-200">
+                    <div className="flex items-center gap-2 mb-2">
+                      <span className="text-sm font-medium text-slate-700">⚠️ 空值/NA 处理</span>
+                      <span className="text-xs text-slate-500">
+                        检测到 {naCount} 个空值
+                      </span>
+                    </div>
+                    <Select
+                      value={naHandling}
+                      onChange={setNaHandling}
+                      style={{ width: '100%' }}
+                      size="small"
+                    >
+                      <Select.Option value="keep">
+                        <span className="text-sm">保持为NA（默认）</span>
+                      </Select.Option>
+                      <Select.Option value="map">
+                        <span className="text-sm">映射为指定值</span>
+                      </Select.Option>
+                      <Select.Option value="drop">
+                        <span className="text-sm text-red-600">删除包含NA的行</span>
+                      </Select.Option>
+                    </Select>
+                    
+                    {naHandling === 'map' && (
+                      <div className="mt-2">
+                        <Input
+                          placeholder="输入NA映射的值（如：9, 未知）"
+                          value={naValue}
+                          onChange={(e) => setNaValue(e.target.value)}
+                          size="small"
+                          prefix={<span className="text-xs text-slate-500">NA → </span>}
+                        />
+                      </div>
+                    )}
+                  </div>
+                )}
               </>
             )}
           </>

frontend-v2/src/modules/dc/pages/tool-c/index.tsx

@@ -36,6 +36,7 @@ interface ToolCState {
   // UI状态
   isLoading: boolean;
   isSidebarOpen: boolean;
+  isAlertClosed: boolean; // ✨ 新增：提示条关闭状态
   
   // ✨ 功能按钮对话框状态
   filterDialogVisible: boolean;
@@ -69,6 +70,7 @@ const ToolC = () => {
     messages: [],
     isLoading: false,
     isSidebarOpen: true,
+    isAlertClosed: false, // ✨ 初始状态：未关闭
     filterDialogVisible: false,
     recodeDialogVisible: false,
     binningDialogVisible: false,
@@ -228,7 +230,7 @@ const ToolC = () => {
 
   // ==================== 渲染 ====================
   return (
-    <div className="h-screen w-screen flex flex-col bg-gradient-to-br from-slate-50 to-slate-100 overflow-hidden">
+    <div className="h-screen w-screen flex flex-col bg-gradient-to-br from-slate-50 to-slate-100">
       {/* 顶部栏 */}
       <Header 
         fileName={state.fileName || '未上传文件'} 
@@ -237,10 +239,10 @@ const ToolC = () => {
         onToggleSidebar={() => updateState({ isSidebarOpen: !state.isSidebarOpen })}
       />
       
-      {/* 主工作区 */}
-      <div className="flex-1 flex overflow-hidden">
-        {/* 左侧：表格区域 */}
-        <div className="flex-1 flex flex-col min-w-0 overflow-hidden">
+      {/* 主工作区 - 移除overflow-hidden，让子元素自己处理滚动 */}
+      <div className="flex-1 flex min-h-0">
+        {/* 左侧：表格区域 - 独立滚动 */}
+        <div className="flex-1 flex flex-col min-w-0">
           <Toolbar 
             sessionId={state.sessionId}
             onFilterClick={() => updateState({ filterDialogVisible: true })}
@@ -251,23 +253,34 @@ const ToolC = () => {
             onComputeClick={() => updateState({ computeDialogVisible: true })}
             onPivotClick={() => updateState({ pivotDialogVisible: true })}
           />
-          <div className="flex-1 p-4 overflow-hidden flex flex-col">
-            {/* ✨ 优化：提示只显示前50行 */}
-            {state.data.length > 0 && (
-              <div className="mb-2 px-3 py-2 bg-blue-50 border border-blue-200 rounded-lg flex items-center gap-2 text-sm">
-                <span className="text-blue-600">ℹ️</span>
-                <span className="text-blue-700">
-                  <strong>提示：</strong>表格仅展示前 <strong>50行</strong> 数据预览，导出功能将包含 <strong>全部</strong> 处理结果
-                </span>
+          <div className="flex-1 p-4 flex flex-col min-h-0">
+            {/* ✨ 优化：提示只显示前50行（可关闭） */}
+            {state.data.length > 0 && !state.isAlertClosed && (
+              <div className="mb-2 px-3 py-2 bg-blue-50 border border-blue-200 rounded-lg flex items-center justify-between gap-2 text-sm">
+                <div className="flex items-center gap-2">
+                  <span className="text-blue-600">ℹ️</span>
+                  <span className="text-blue-700">
+                    <strong>提示：</strong>表格仅展示前 <strong>50行</strong> 数据预览，导出功能将包含 <strong>全部</strong> 处理结果
+                  </span>
+                </div>
+                <button
+                  onClick={() => updateState({ isAlertClosed: true })}
+                  className="text-blue-400 hover:text-blue-600 transition-colors p-1 rounded hover:bg-blue-100"
+                  title="关闭提示"
+                >
+                  <svg width="16" height="16" viewBox="0 0 16 16" fill="currentColor">
+                    <path d="M4.646 4.646a.5.5 0 0 1 .708 0L8 7.293l2.646-2.647a.5.5 0 0 1 .708.708L8.707 8l2.647 2.646a.5.5 0 0 1-.708.708L8 8.707l-2.646 2.647a.5.5 0 0 1-.708-.708L7.293 8 4.646 5.354a.5.5 0 0 1 0-.708z"/>
+                  </svg>
+                </button>
               </div>
             )}
-            <div className="flex-1 overflow-hidden">
+            <div className="flex-1 min-h-0">
               <DataGrid data={state.data} columns={state.columns} />
             </div>
           </div>
         </div>
 
-        {/* 右侧：AI 数据清洗助手 */}
+        {/* 右侧：AI 数据清洗助手 - 独立滚动 */}
         {state.isSidebarOpen && (
           <Sidebar
             isOpen={state.isSidebarOpen}