ref(ai): add stub, fix includes, move aiwin_send_message location

src/ai/ai_client.h

@@ -185,13 +185,10 @@ void ai_session_set_model(AISession* session, const gchar* model);
  * Send a prompt to the AI provider asynchronously.
  * @param session The AI session containing provider and model
  * @param prompt The prompt to send
- * @param response_cb Callback function for successful responses
- * @param error_cb Callback function for error handling
  * @param user_data User data to be passed to the callbacks
  * @return TRUE if the request was successfully queued, FALSE otherwise
  */
 gboolean ai_send_prompt(AISession* session, const gchar* prompt,
-                        ai_response_cb response_cb, ai_error_cb error_cb,
                         gpointer user_data);
 
 /**