fix(gateway): clear stale pending model note on session reset

gateway/run.py

@@ -5313,6 +5313,8 @@ class GatewayRunner:
         # picks up configured defaults instead of previous session switches.
         self._session_model_overrides.pop(session_key, None)
         self._set_session_reasoning_override(session_key, None)
+        if hasattr(self, "_pending_model_notes"):
+            self._pending_model_notes.pop(session_key, None)
 
         # Clear session-scoped dangerous-command approvals and /yolo state.
         # /new is a conversation-boundary operation — approval state from the