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/blackboard/operations.py

@@ -11,7 +11,6 @@ from typing import Any, Dict, List, Optional
 
 from .db import (
     VALID_TRANSITIONS,
-    VALID_STATUSES,
     COMMENT_TYPES,
     EVENT_TYPES,
     OUTPUT_TYPES,
@@ -84,7 +83,8 @@ class Blackboard:
         """获取单个任务"""
         conn = self._conn()
         try:
-            row = conn.execute("SELECT * FROM tasks WHERE id=?", (task_id,)).fetchone()
+            row = conn.execute(
+                "SELECT * FROM tasks WHERE id=?", (task_id,)).fetchone()
             return Task.from_row(row) if row else None
         finally:
             conn.close()
@@ -129,7 +129,8 @@ class Blackboard:
                 updates["completed_at"] = now  # paused 也记录时间用于恢复
                 updates["resumed_from"] = old_status  # 记录暂停前状态
             elif new_status == "pending":
-                # 所有 →pending 转换都清空 assignee（与 ticker._transition_status L414 对齐）
+                # 所有 →pending 转换都清空 assignee（与 ticker._transition_status L414
+                # 对齐）
                 updates["assignee"] = None
                 updates["claimed_at"] = None
                 updates["current_agent"] = None
@@ -693,7 +694,6 @@ class Blackboard:
         finally:
             conn.close()
 
-
     # ── Checkpoint CRUD（M3） ──
 
     def create_checkpoint(
@@ -709,7 +709,8 @@ class Blackboard:
         import uuid
         # BUG-33: 校验 payload 结构必须含 version 字段
         if not isinstance(payload, dict) or "version" not in payload:
-            raise ValueError("payload must be a dict containing 'version' field")
+            raise ValueError(
+                "payload must be a dict containing 'version' field")
         cp_id = checkpoint_id or f"cp-{uuid.uuid4().hex[:8]}"
         conn = self._conn()
         try:
@@ -966,7 +967,8 @@ class Blackboard:
         finally:
             conn.close()
 
-    def get_pending_mentions(self, max_retries: int = 5) -> List[Dict[str, Any]]:
+    def get_pending_mentions(
+            self, max_retries: int = 5) -> List[Dict[str, Any]]:
         """获取所有 pending 且未超过重试上限的 mentions"""
         conn = self._conn()
         try:
@@ -1001,7 +1003,8 @@ class Blackboard:
         conn = self._conn()
         try:
             conn.execute("BEGIN IMMEDIATE")
-            conn.execute("UPDATE mention_queue SET retry_count=retry_count+1 WHERE id=?", (mention_id,))
+            conn.execute(
+                "UPDATE mention_queue SET retry_count=retry_count+1 WHERE id=?", (mention_id,))
             conn.commit()
             return True
         finally:
@@ -1012,7 +1015,8 @@ class Blackboard:
         conn = self._conn()
         try:
             conn.execute("BEGIN IMMEDIATE")
-            conn.execute("UPDATE mention_queue SET status='failed' WHERE id=?", (mention_id,))
+            conn.execute(
+                "UPDATE mention_queue SET status='failed' WHERE id=?", (mention_id,))
             conn.commit()
             return True
         finally: