refactor: reorganize startup persistence boundaries

app/startup/initializers/monitor.py

@@ -0,0 +1,26 @@
+from app.monitor import Monitor
+from app.runtime.execution import run_in_threadpool_to_completion
+
+
+def init_monitor() -> None:
+    """初始化监控器；复用单例时必须显式开启新的应用 lifespan。"""
+    monitor = Monitor.get_existing_instance()
+    if monitor is None:
+        Monitor()
+        return
+    if not monitor.lifecycle_closed:
+        return
+    if not monitor.reopen(timeout=Monitor.RELOAD_STOP_TIMEOUT):
+        raise RuntimeError("旧目录监控 owner 未收敛，无法开启新生命周期")
+    if not monitor.init(timeout=Monitor.RELOAD_STOP_TIMEOUT):
+        raise RuntimeError("目录监控初始化失败")
+
+
+async def stop_monitor(timeout: float = Monitor.LIFECYCLE_CLOSE_TIMEOUT) -> bool:
+    """在线程池里永久关闭监控器，取消后仍等待同步 owner 收敛到终态。"""
+    monitor = Monitor.get_existing_instance()
+    if monitor is None:
+        return True
+    return bool(
+        await run_in_threadpool_to_completion(monitor.close, timeout=timeout)
+    )