feat: Step 5 引擎接入 + H1-H3/S3 修复 + 审计 D1/D2/D5 修复

引擎接入（dispatcher/spawner/ticker → handler 统一路由）:
- dispatcher: guardrail/on_checks_passed/on_complete → handler 查询
- spawner: _build_prompt/_build_api_section → handler.build_prompt
- ticker: 虚拟项目扫描/assignee/claimed/review/幻觉门控 → handler 判断

Handler 缺陷修复:
- H1: _mark_task_status 加 3 次重试（防 DB 锁）
- H2: review @mention 加 comment_type='review'
- H3: review 非 approved 保持 review 状态（不标 working）
- S3: 通知链接改 Gitea（PR/Issue/Commit）

审计修复:
- D1: pre_spawn 返回值未检查 → 加 if not 抛 RuntimeError
- D2: PromptContext 缺 from_agent/mail_type → 从 must_haves 解析
- D5: _check_reply 查错表 → 恢复查 tasks 表找 in_reply_to

旧方法保留未删（deprecated），确认稳定后再清理。

src/daemon/spawner.py

@@ -278,10 +278,30 @@ class AgentSpawner:
                 task_id, title, description, must_haves,
                 project_id, agent_id)
 
-        # mail 任务用精简模板
-        if project_id == "_mail":
-            return self._build_mail_prompt(
-                task_id, title, description, must_haves, agent_id)
+        # handler 路径：Task/Mail/Toolchain 用各自的 PromptSection 构建
+        from src.daemon.task_type_registry import TaskTypeRegistry
+        handler = TaskTypeRegistry.get_by_project(project_id)
+        if handler:
+            from src.daemon.prompt_composer import PromptContext
+            # 从 must_haves 解析 mail 元数据（from / performative）
+            from_agent = ""
+            mail_type = ""
+            try:
+                meta = json.loads(must_haves) if must_haves else {}
+                from_agent = meta.get("from", "")
+                mail_type = meta.get("performative", meta.get("type", ""))
+            except Exception:
+                pass
+            ctx = PromptContext(
+                task_id=task_id, title=title, description=description or "",
+                must_haves=must_haves or "", project_id=project_id,
+                agent_id=agent_id, role=spawn_type,
+                spawn_type=spawn_type,
+                from_agent=from_agent, mail_type=mail_type,
+            )
+            return handler.build_prompt(ctx)
+
+        # 旧路径保留：_general 等非 handler 项目
 
         # 走 BootstrapBuilder 新路径
         if self.bootstrap_builder and task is not None:
@@ -321,8 +341,14 @@ class AgentSpawner:
     def _build_api_section(self, project_id: str, task_id: str,
                            agent_id: str) -> str:
         """构建 API 回写操作指令(BootstrapBuilder 模式下补充)"""
-        # mail 任务直接 done,不走 review
-        success_status = '"done"' if project_id == "_mail" else '"review"'
+        # handler 项目（_mail/_toolchain）的 success_status 由 PromptSection 处理
+        # 这里只处理无 handler 的项目（normal task）
+        from src.daemon.task_type_registry import TaskTypeRegistry
+        handler = TaskTypeRegistry.get_by_project(project_id)
+        if handler:
+            success_status = '"done"' if handler.target_success_status == "done" else '"review"'
+        else:
+            success_status = '"review"'
         return f"""## 操作指令
 
 ### 状态回写