fix(qqbot): add backoff upper-bound check for QQCloseError reconnect path

The QQCloseError (non-4008) reconnect path in _listen_loop was
missing the MAX_RECONNECT_ATTEMPTS upper-bound check that exists
in both the Exception handler (line 546) and the 4008 rate-limit
handler (line 486). Without this check, if _reconnect() fails
permanently for any non-4008 close code, backoff_idx grows
indefinitely and the bot retries forever at 60-second intervals
instead of giving up cleanly.

Fix: add the same guard after backoff_idx += 1 in the general
QQCloseError branch, consistent with the existing Exception path.

gateway/platforms/qqbot/adapter.py

@@ -535,6 +535,9 @@ class QQAdapter(BasePlatformAdapter):
                     quick_disconnect_count = 0
                 else:
                     backoff_idx += 1
+                    if backoff_idx >= MAX_RECONNECT_ATTEMPTS:
+                        logger.error("[%s] Max reconnect attempts reached (QQCloseError)", self._log_tag)
+                        return
 
             except Exception as exc:
                 if not self._running: