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/counter.py

@@ -68,20 +68,23 @@ class ActiveAgentCounter:
         self._cooldown_until.pop(agent_id, None)
         return False
 
-    def set_cooldown(self, agent_id: str, seconds: Optional[float] = None) -> None:
+    def set_cooldown(self, agent_id: str,
+                     seconds: Optional[float] = None) -> None:
         """设置冷却期（默认 120 秒）"""
         cd = seconds if seconds is not None else self._default_cooldown_seconds
         self._cooldown_until[agent_id] = time.time() + cd
         logger.info("Cooldown set for %s: %.0fs (until %.0f)",
-                     agent_id, cd, self._cooldown_until[agent_id])
+                    agent_id, cd, self._cooldown_until[agent_id])
 
-    async def can_acquire(self, agent_id: str, session_id: str = "main") -> bool:
+    async def can_acquire(self, agent_id: str,
+                          session_id: str = "main") -> bool:
         """三层检查：cooldown → global → per agent → per session key"""
         if self.is_cooling_down(agent_id):
             return False
         if self._global_active >= self._max_global:
             return False
-        if self._agent_active.get(agent_id, 0) >= self._max_concurrent_sessions:
+        if self._agent_active.get(
+                agent_id, 0) >= self._max_concurrent_sessions:
             return False
         key = self._make_key(agent_id, session_id)
         if self._active_keys.get(key, 0) >= self._max_per_session:
@@ -122,7 +125,8 @@ class ActiveAgentCounter:
                 del self._active_keys[key]
 
         if agent_id in self._agent_active:
-            self._agent_active[agent_id] = max(0, self._agent_active[agent_id] - 1)
+            self._agent_active[agent_id] = max(
+                0, self._agent_active[agent_id] - 1)
             if self._agent_active[agent_id] == 0:
                 del self._agent_active[agent_id]