feat(ssa): SSA Agent mode MVP - prompt management + Phase 5A guardrails + UX enhancements

Backend:
- Agent core prompts (Planner + Coder) now loaded from PromptService with 3-tier fallback (DB -> cache -> hardcoded)
- Seed script (seed-ssa-agent-prompts.ts) for idempotent SSA_AGENT_PLANNER + SSA_AGENT_CODER setup
- SSA fallback prompts added to prompt.fallbacks.ts
- Phase 5A: XML tag extraction, defensive programming prompt, high-fidelity schema injection, AST pre-check
- Default agent mode migration + session CRUD (rename/delete) APIs
- R Docker: structured error handling (20+ patterns) + AST syntax pre-check

Frontend:
- Default agent mode (QPER toggle removed), view code fix, analysis result cards in chat
- Session history sidebar with inline rename/delete, robust plan parsing from reviewResult
- R code export wrapper for local reproducibility (package checks + data loader + polyfills)
- SSA workspace CSS updates for sidebar actions and plan display

Docs:
- SSA module doc v4.2: Prompt inventory (2 Agent active / 11 QPER archived), dev progress updated
- System overview doc v6.8: SSA Agent MVP milestone
- Deployment checklist: DB-5 (seed script) + BE-10 (prompt management)

Made-with: Cursor

backend/src/modules/ssa/routes/chat.routes.ts

@@ -115,12 +115,8 @@ export default async function chatRoutes(app: FastifyInstance) {
       }
       // ── H1 结束 ──
 
-      // 3. 读取 session 的执行模式
-      const session = await (prisma.ssaSession as any).findUnique({
-        where: { id: sessionId },
-        select: { executionMode: true },
-      });
-      const executionMode = (session?.executionMode as string) || 'qper';
+      // 3. 执行模式：统一使用 Agent 通道（QPER 已废弃 UI 入口）
+      const executionMode = 'agent';
 
       // ── Agent 通道分流 ──
       if (executionMode === 'agent') {

backend/src/modules/ssa/routes/session.routes.ts

@@ -50,7 +50,9 @@ export default async function sessionRoutes(app: FastifyInstance) {
       if (data) {
         const buffer = await data.toBuffer();
         const filename = data.filename;
-        title = filename;
+        const baseName = filename.replace(/\.(csv|xlsx?)$/i, '') || '数据';
+        const now = new Date();
+        title = `${baseName} ${now.getMonth() + 1}月${now.getDate()}日`;
         
         // 生成存储 Key（遵循 OSS 目录结构规范）
         const uuid = crypto.randomUUID().replace(/-/g, '').substring(0, 16);
@@ -113,20 +115,45 @@ export default async function sessionRoutes(app: FastifyInstance) {
     
     const sessions = await prisma.ssaSession.findMany({
       where: { userId },
-      orderBy: { createdAt: 'desc' },
-      take: 20
+      orderBy: { updatedAt: 'desc' },
+      take: 30,
+      select: {
+        id: true,
+        title: true,
+        status: true,
+        executionMode: true,
+        createdAt: true,
+        updatedAt: true,
+      },
     });
     
-    return reply.send(sessions);
+    return reply.send({ sessions });
   });
 
-  // 获取会话详情
+  // 获取会话详情（含 Agent 执行历史）
   app.get('/:id', async (req, reply) => {
     const { id } = req.params as { id: string };
     
     const session = await prisma.ssaSession.findUnique({
       where: { id },
-      include: { messages: true }
+      include: {
+        agentExecutions: {
+          orderBy: { createdAt: 'asc' },
+          select: {
+            id: true,
+            query: true,
+            planText: true,
+            reviewResult: true,
+            generatedCode: true,
+            reportBlocks: true,
+            retryCount: true,
+            status: true,
+            errorMessage: true,
+            durationMs: true,
+            createdAt: true,
+          },
+        },
+      },
     });
     
     if (!session) {
@@ -136,6 +163,60 @@ export default async function sessionRoutes(app: FastifyInstance) {
     return reply.send(session);
   });
 
+  /**
+   * PATCH /sessions/:id
+   * 更新会话（当前仅支持 title）
+   */
+  app.patch('/:id', async (req, reply) => {
+    const userId = getUserId(req);
+    const { id } = req.params as { id: string };
+    const body = req.body as { title?: string };
+
+    const session = await prisma.ssaSession.findUnique({ where: { id } });
+    if (!session) {
+      return reply.status(404).send({ error: 'Session not found' });
+    }
+    if (session.userId !== userId) {
+      return reply.status(403).send({ error: 'Forbidden' });
+    }
+
+    const data: { title?: string } = {};
+    if (typeof body.title === 'string' && body.title.trim()) {
+      data.title = body.title.trim();
+    }
+    if (Object.keys(data).length === 0) {
+      return reply.send(session);
+    }
+
+    const updated = await prisma.ssaSession.update({
+      where: { id },
+      data,
+    });
+    logger.info('[SSA:Session] Session updated', { sessionId: id, title: data.title });
+    return reply.send(updated);
+  });
+
+  /**
+   * DELETE /sessions/:id
+   * 删除会话（级联删除消息、执行记录等）
+   */
+  app.delete('/:id', async (req, reply) => {
+    const userId = getUserId(req);
+    const { id } = req.params as { id: string };
+
+    const session = await prisma.ssaSession.findUnique({ where: { id } });
+    if (!session) {
+      return reply.status(404).send({ error: 'Session not found' });
+    }
+    if (session.userId !== userId) {
+      return reply.status(403).send({ error: 'Forbidden' });
+    }
+
+    await prisma.ssaSession.delete({ where: { id } });
+    logger.info('[SSA:Session] Session deleted', { sessionId: id });
+    return reply.send({ success: true });
+  });
+
   /**
    * PATCH /sessions/:id/execution-mode
    * 切换双通道执行模式 (qper / agent)