refactor(vscode-ide-companion): 优化代码结构和性能

- 移除未使用的依赖项 qwen-code
- 优化 completion 刷新逻辑，避免渲染循环
- 更新 CompletionMenu 组件，增加空状态提示

packages/vscode-ide-companion/src/webview/App.tsx

@@ -138,11 +138,16 @@ export const App: React.FC = () => {
   const completion = useCompletionTrigger(inputFieldRef, getCompletionItems);
 
   // When workspace files update while menu open for @, refresh items so the first @ shows the list
+  // Note: Avoid depending on the entire `completion` object here, since its identity
+  // changes on every render which would retrigger this effect and can cause a refresh loop.
   useEffect(() => {
     if (completion.isOpen && completion.triggerChar === '@') {
+      // Only refresh items; do not change other completion state to avoid re-renders loops
       completion.refreshCompletion();
     }
-  }, [fileContext.workspaceFiles, completion]);
+    // Only re-run when the actual data source changes, not on every render
+    // eslint-disable-next-line react-hooks/exhaustive-deps
+  }, [fileContext.workspaceFiles, completion.isOpen, completion.triggerChar]);
 
   // Message submission
   const handleSubmit = useMessageSubmit({