fix: M2 on_failure assignee 从 tasks 表读取 + infrastructure 防递归（司马懿 Review #65）

M2: on_failure 中 assignee = meta.get('from', '') 读到 'system' 而非实际 Agent
→ 改为 SELECT must_haves, assignee FROM tasks 直接读 tasks.assignee 字段

附带：infrastructure failure 改为直接 DB INSERT，不走 _send_toolchain_task 防递归

src/daemon/toolchain_handler.py

@@ -297,22 +297,24 @@ class ToolchainHandler(BaseTaskHandler):
         logger.info("Toolchain %s: verify failed (%s), marked failed",
                     task_id, verify.reason)
 
-        # 读取 must_haves 获取事件上下文
+        # 读取 must_hives 获取事件上下文 + assignee 从 tasks 表读取
         meta = {}
+        assignee = agent_id
         try:
             conn = get_connection(db_path)
             row = conn.execute(
-                "SELECT must_haves FROM tasks WHERE id=?", (task_id,)
+                "SELECT must_haves, assignee FROM tasks WHERE id=?", (task_id,)
             ).fetchone()
-            if row and row["must_haves"]:
-                meta = json.loads(row["must_haves"])
+            if row:
+                if row["must_haves"]:
+                    meta = json.loads(row["must_haves"])
+                assignee = row["assignee"] or agent_id
             conn.close()
         except Exception:
             pass
 
         action_type = meta.get("action_type", "")
         context_data = meta.get("context", {})
-        assignee = meta.get("assignee", "") or meta.get("from", "")
 
         # 三分路决策
         route = self._classify_failure(verify)
@@ -403,29 +405,43 @@ class ToolchainHandler(BaseTaskHandler):
         self, task_id: str, agent_id: str,
         verify: VerifyResult, db_path: Path,
     ) -> None:
-        """基础设施失败 → _send_toolchain_task @jiangwei-infra(防递归)"""
-        # 直接在 _toolchain DB 创建 task(不走 Gitea webhook)
+        """基础设施失败 → 直接在 _toolchain DB 创建 task @jiangwei-infra（防递归）"""
         try:
-            from src.api.toolchain_routes import _send_toolchain_task
-            _send_toolchain_task(
-                to_agent="jiangwei-infra",
-                title=f"[基础设施] Gitea API 不可用 - {task_id}",
-                description=(
-                    f"Gitea API 不可用,原任务 {task_id} 无法通过正常路径处理。\n"
-                    f"请检查 Gitea 服务状态和网络连通性。"
-                ),
-                event_type="infrastructure_failure",
-                action_type="infrastructure_failure",
-                steps=[
+            from datetime import datetime
+            new_task_id = f"tc-{int(datetime.now().timestamp() * 1000)}"
+            must_hives = json.dumps({
+                "event_type": "infrastructure_failure",
+                "action_type": "infrastructure_failure",
+                "steps": [
                     "检查 Gitea 服务状态(http://192.168.2.154:3000)",
                     "检查网络连通性",
                     "恢复后提交 action report",
                 ],
-                context_data={"original_task_id": task_id, "verify_reason": verify.reason},
-                source="toolchain_handler",
+                "context": {"original_task_id": task_id, "verify_reason": verify.reason},
+                "from": "system",
+                "source": "toolchain_handler_on_failure",
+            }, ensure_ascii=False)
+            conn = get_connection(db_path)
+            conn.execute(
+                "INSERT INTO tasks (id, title, description, assignee, assigned_by, "
+                "must_haves, task_type, status) VALUES (?, ?, ?, ?, ?, ?, ?, ?)",
+                (
+                    new_task_id,
+                    f"[基础设施] Gitea API 不可用 - {task_id}",
+                    f"Gitea API 不可用,原任务 {task_id} 无法通过正常路径处理。\n"
+                    f"请检查 Gitea 服务状态和网络连通性。",
+                    "jiangwei-infra",
+                    "system",
+                    must_hives,
+                    "toolchain",
+                    "pending",
+                )
             )
-            logger.info("Toolchain %s: infrastructure failure → task created for jiangwei-infra",
-                        task_id)
+            conn.commit()
+            conn.close()
+            logger.info(
+                "Toolchain %s: infrastructure failure → task %s created for jiangwei-infra",
+                task_id, new_task_id)
         except Exception as e:
             logger.error(
                 "Toolchain %s: failed to create infrastructure_failure task: %s",