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/base_task_handler.py

@@ -127,32 +127,35 @@ class BaseTaskHandler:
                            task_id, e)
     
     def _mark_task_status(self, db_path: Path, task_id: str, status: str) -> None:
-        """更新任务状态 + 写审计事件。
-        从 dispatcher._mark_task_status 迁移。"""
-        try:
-            conn = get_connection(db_path)
+        """更新任务状态 + 写审计事件（带 3 次重试，防 SQLite DB 锁）。"""
+        for attempt in range(3):
             try:
-                conn.execute("BEGIN IMMEDIATE")
-                old_row = conn.execute(
-                    "SELECT status FROM tasks WHERE id=?", (task_id,)
-                ).fetchone()
-                old_status = old_row["status"] if old_row else "unknown"
-                conn.execute(
-                    "UPDATE tasks SET status=?, updated_at=datetime('now') WHERE id=?",
-                    (status, task_id),
-                )
-                conn.execute(
-                    "INSERT INTO events (task_id, agent, event_type, payload) "
-                    "VALUES (?, 'handler', 'status_change', ?)",
-                    (task_id,
-                     f'{{"from": "{old_status}", "to": "{status}", '
-                     f'"source": "{self.task_type}_handler"}}'),
-                )
-                conn.commit()
-            finally:
-                conn.close()
-        except Exception as e:
-            logger.error("Task %s: mark status error: %s", task_id, e)
+                conn = get_connection(db_path)
+                try:
+                    conn.execute("BEGIN IMMEDIATE")
+                    old_row = conn.execute(
+                        "SELECT status FROM tasks WHERE id=?", (task_id,)
+                    ).fetchone()
+                    old_status = old_row["status"] if old_row else "unknown"
+                    conn.execute(
+                        "UPDATE tasks SET status=?, updated_at=datetime('now') WHERE id=?",
+                        (status, task_id),
+                    )
+                    conn.execute(
+                        "INSERT INTO events (task_id, agent, event_type, payload) "
+                        "VALUES (?, 'handler', 'status_change', ?)",
+                        (task_id,
+                         f'{{"from": "{old_status}", "to": "{status}", '
+                         f'"source": "{self.task_type}_handler"}}'),
+                    )
+                    conn.commit()
+                    return
+                finally:
+                    conn.close()
+            except Exception as e:
+                logger.warning("Handler: mark %s → %s attempt %d failed: %s",
+                               task_id, status, attempt + 1, e)
+        logger.error("Handler: mark %s → %s all 3 attempts failed", task_id, status)
     
     def _auto_mark_working(self, task_id: str, db_path: Path) -> bool:
         """pending → working（mail/toolchain 通用）。"""