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>

tests/gateway/test_qqbot.py

@@ -2196,3 +2196,27 @@ class TestCloseCodeClassification:
         assert 4014 in fatal_codes
         assert 4001 in fatal_codes
         assert 4915 in fatal_codes
+
+
+class TestReadEventsClosedWsGuard:
+    """Regression: a closed-but-non-None ws must raise on entry, not return
+    normally, so _listen_loop goes through reconnect/backoff instead of
+    busy-looping at 100% CPU (issues #31193 / #31771)."""
+
+    def _make_adapter(self, **extra):
+        from gateway.platforms.qqbot import QQAdapter
+        return QQAdapter(_make_config(app_id="a", client_secret="b", **extra))
+
+    def test_read_events_raises_when_ws_closed_on_entry(self):
+        adapter = self._make_adapter()
+        adapter._running = True
+        adapter._ws = SimpleNamespace(closed=True)
+        with pytest.raises(RuntimeError):
+            asyncio.run(adapter._read_events())
+
+    def test_read_events_raises_when_ws_none(self):
+        adapter = self._make_adapter()
+        adapter._running = True
+        adapter._ws = None
+        with pytest.raises(RuntimeError):
+            asyncio.run(adapter._read_events())