fix(multimodal): harden playback and client lifecycle handling

- retry the server connection prompt after transient playback failures
- serialize multimodal client and session start-stop operations
- tag downstream responses to ignore stale packets and playback events
- complete bounded teardown and clean callbacks after partial startup

components/control_plane/src/runtime/control_plane_runtime_workers.c

@@ -1777,7 +1777,7 @@ static void control_plane_wifi_state_task(void *arg)
 
             if (!disconnected_expression_active) {
                 ESP_LOGI(TAG, "Wi-Fi STA disconnect persisted; stopping multimodal client");
-                control_plane_stop_multimodal_client();
+                (void)control_plane_stop_multimodal_client();
                 control_plane_stop_user_config_server();
             }
 
@@ -2455,7 +2455,7 @@ void control_plane_stop_runtime_workers(void)
     portEXIT_CRITICAL(&s_runtime_lock);
     control_plane_delete_model_cmd_queue(queue, queue_with_caps);
 
-    control_plane_stop_multimodal_client();
+    (void)control_plane_stop_multimodal_client();
     control_plane_set_runtime_stop_requested(false);
 }