fix(agent): implement AgentProtocol disposal to prevent memory leaks

packages/cli/src/ui/AppContainer.tsx

@@ -1180,6 +1180,10 @@ Logging in with Google... Restarting Gemini CLI to continue.
     [config, getPreferredEditor],
   );
 
+  useEffect(() => () => {
+      streamAgent?.dispose?.();
+    }, [streamAgent]);
+
   const activeStream = streamAgent
     ? // eslint-disable-next-line react-hooks/rules-of-hooks
       useAgentStream({