feat: Enhance AgentChatWidget with Improved Message Handling and UI Updates

- Updated the AgentChatWidget to manage AI response states, including a new mechanism for handling pending messages and a thinking animation indicator.
- Improved the initialization of embedded labels for resource tools, ensuring labels are loaded only when necessary, enhancing performance and user experience.
- Refined the chat history synchronization process to ensure timely updates in the chat history popup.
- Enhanced the UI layout for better readability and interaction, including adjustments to button styles and spacing for a more polished appearance.

src/app/editor/agent/agent_chat_widget.h

@@ -235,6 +235,11 @@ public:
   // History synchronization
   void SyncHistoryToPopup();
 
+  // AI response state
+  bool waiting_for_response_ = false;
+  float thinking_animation_ = 0.0f;
+  std::string pending_message_;
+  
   // Chat session management
   struct ChatSession {
     std::string id;