fix(lint): 修复 PR #14 引入的 lint 回退 (119→0)

PR #14 从旧分支复制文件导致回退了 PR #10 的 lint 修复。
修复内容:
- autoflake 移除未使用导入/变量
- autopep8 修复缩进/空格
- 手动修复 F821(pathlib→Path), F541(f-string), F841(未使用变量)
- 所有修复均通过 flake8 --max-line-length=120 --extend-ignore=E501 检查 (0 errors)

src/daemon/mail_notify.py

@@ -50,7 +50,9 @@ def notify_mail_failed(db_path: Path, original_mail_id: str,
         bb = Blackboard(db_path)
         original = bb.get_task(original_mail_id)
         if not original:
-            logger.warning("notify_mail_failed: original mail %s not found", original_mail_id)
+            logger.warning(
+                "notify_mail_failed: original mail %s not found",
+                original_mail_id)
             return
 
         # 解析原邮件元数据
@@ -58,7 +60,9 @@ def notify_mail_failed(db_path: Path, original_mail_id: str,
 
         # 防递归：系统通知邮件失败不再发通知
         if meta.get("system_notify"):
-            logger.info("Mail %s: system notify mail failed, skipping recursive notification", original_mail_id)
+            logger.info(
+                "Mail %s: system notify mail failed, skipping recursive notification",
+                original_mail_id)
             return
 
         # 获取发件人（优先 assigned_by，fallback must_haves.from）
@@ -67,7 +71,9 @@ def notify_mail_failed(db_path: Path, original_mail_id: str,
         title = original.title or ""
 
         if not from_agent:
-            logger.warning("notify_mail_failed: cannot determine sender for mail %s", original_mail_id)
+            logger.warning(
+                "notify_mail_failed: cannot determine sender for mail %s",
+                original_mail_id)
             return
 
         # 发件人不是有效 Agent（如 system）→ 通知庞统代处理，不触发广播
@@ -108,7 +114,10 @@ def notify_mail_failed(db_path: Path, original_mail_id: str,
         )
         bb.create_task(notify_task)
         logger.info("Mail %s: sent failure notification to %s (original_sender=%s, reason=%s, notify_id=%s)",
-                     original_mail_id, target_agent, from_agent, reason, notify_id)
+                    original_mail_id, target_agent, from_agent, reason, notify_id)
 
     except Exception as e:
-        logger.warning("notify_mail_failed: failed to send notification for mail %s: %s", original_mail_id, e)
+        logger.warning(
+            "notify_mail_failed: failed to send notification for mail %s: %s",
+            original_mail_id,
+            e)