Document SDK turn routing helpers

Co-authored-by: Codex <noreply@openai.com>

sdk/python/src/codex_app_server/_message_router.py

@@ -22,6 +22,7 @@ class MessageRouter:
     """
 
     def __init__(self) -> None:
+        """Create empty response, turn, and global notification queues."""
         self._lock = threading.Lock()
         self._response_waiters: dict[str, queue.Queue[ResponseQueueItem]] = {}
         self._turn_notifications: dict[str, queue.Queue[NotificationQueueItem]] = {}
@@ -144,6 +145,7 @@ class MessageRouter:
         self._global_notifications.put(exc)
 
     def _notification_turn_id(self, notification: Notification) -> str | None:
+        """Extract routing ids from known generated payloads or raw unknown payloads."""
         payload = notification.payload
         if isinstance(payload, UnknownNotification):
             raw_turn_id = payload.params.get("turnId")