fix(qqbot): stop 100% CPU spin when WebSocket is closed but not None (#31193, #31771) (#40574)

_read_events() returned normally when self._ws was closed-but-non-None
(the while-condition is false on entry). _listen_loop treats a normal
return as a clean read, resets backoff to 0, and immediately retries —
a tight busy-loop pinning CPU. Raising on entry routes it through the
reconnect/backoff path instead.

Co-authored-by: xushibo <xushibo@users.noreply.github.com>
Co-authored-by: cnfi <cnfi@users.noreply.github.com>

gateway/platforms/qqbot/adapter.py

@@ -681,6 +681,12 @@ class QQAdapter(BasePlatformAdapter):
         """Read WebSocket frames until connection closes."""
         if not self._ws:
             raise RuntimeError("WebSocket not connected")
+        if self._ws.closed:
+            # A closed-but-non-None ws makes the while-condition false on entry,
+            # so this would return normally — which _listen_loop treats as a
+            # clean read and immediately retries with backoff reset to 0,
+            # producing a 100% CPU spin. Raise so the reconnect/backoff path runs.
+            raise RuntimeError("WebSocket closed")
 
         while self._running and self._ws and not self._ws.closed:
             msg = await self._ws.receive()