fix(dc-tool-b): 修复滚动条问题 - 适配MainLayout固定高度

- tool-b/index.tsx: min-h-screen  h-full overflow-y-auto
- 所有Step组件添加 h-full overflow-y-auto
- 修复：MainLayout改为固定高度后，工具B底部按钮可见性问题
- 效果：页面无滚动条，内容可内部滚动

frontend-v2/src/modules/dc/pages/tool-b/Step1Upload.tsx

@@ -113,7 +113,7 @@ const Step1Upload: React.FC<Step1UploadProps> = ({ state, updateState, onNext })
   const canProceed = state.healthCheckResult.status === 'good';
 
   return (
-    <div className="max-w-3xl mx-auto w-full space-y-8 animate-in fade-in slide-in-from-bottom-4 duration-500 mt-8">
+    <div className="max-w-3xl mx-auto w-full space-y-8 animate-in fade-in slide-in-from-bottom-4 duration-500 mt-8 h-full overflow-y-auto">
       {/* 文件上传区域 */}
       {!state.fileName ? (
         <div className="border-2 border-dashed border-slate-300 rounded-xl p-12 text-center hover:border-purple-400 hover:bg-purple-50/30 transition-all cursor-pointer">

frontend-v2/src/modules/dc/pages/tool-b/Step2Schema.tsx

@@ -80,7 +80,7 @@ const Step2Schema: React.FC<Step2SchemaProps> = ({ state, updateState, onNext, o
   };
 
   return (
-    <div className="max-w-5xl mx-auto w-full space-y-6 animate-in fade-in slide-in-from-right-4 duration-500 mt-4">
+    <div className="max-w-5xl mx-auto w-full space-y-6 animate-in fade-in slide-in-from-right-4 duration-500 mt-4 h-full overflow-y-auto">
       {/* 模板选择 */}
       <div className="bg-purple-50 p-6 rounded-xl border border-purple-100 grid grid-cols-2 gap-6">
         <div>

frontend-v2/src/modules/dc/pages/tool-b/Step3Processing.tsx

@@ -108,7 +108,7 @@ const Step3Processing: React.FC<Step3ProcessingProps> = ({ state, updateState, o
   }, []);
 
   return (
-    <div className="max-w-4xl mx-auto w-full space-y-6 animate-in fade-in slide-in-from-bottom-4 duration-500 mt-8">
+    <div className="max-w-4xl mx-auto w-full space-y-6 animate-in fade-in slide-in-from-bottom-4 duration-500 mt-8 h-full overflow-y-auto">
       <div className="text-center">
         <h3 className="text-xl font-bold text-slate-900 mb-2">双模型提取交叉验证中...</h3>
         <p className="text-sm text-slate-500">DeepSeek-V3 & Qwen-Max 双引擎协同工作</p>

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

@@ -73,7 +73,7 @@ const ToolBModule: React.FC = () => {
   };
 
   return (
-    <div className="min-h-screen bg-slate-50 font-sans text-slate-800 p-6">
+    <div className="h-full bg-slate-50 font-sans text-slate-800 p-6 overflow-y-auto">
       <div className="max-w-7xl mx-auto bg-white rounded-2xl shadow-sm border border-slate-200 min-h-[800px] flex flex-col overflow-hidden">
         
         {/* Header */}
@@ -123,8 +123,8 @@ const ToolBModule: React.FC = () => {
           <StepIndicator currentStep={currentStep} />
         </div>
 
-        {/* Main Content */}
-        <div className="flex-1 px-8 pb-8 relative overflow-hidden flex flex-col">
+        {/* Main Content - ⭐ 修复：添加overflow-y-auto允许内部滚动 */}
+        <div className="flex-1 px-8 pb-8 relative overflow-y-auto flex flex-col">
           {currentStep === 'upload' && (
             <Step1Upload
               state={state}