Fix TypeScript errors in designer-modes example

- Remove unnecessary React import from App.tsx (jsx: react-jsx handles JSX automatically)
- Update main.tsx to use named imports instead of namespace import
- Add vite/client types to tsconfig for CSS import support

Fixes TS6133 and TS2307 errors that were causing CI build failures

Co-authored-by: huangyiirene <7665279+huangyiirene@users.noreply.github.com>

Author: Copilot

examples/designer-modes/src/App.tsx

@@ -1,4 +1,4 @@
-import React, { useState } from 'react';
+import { useState } from 'react';
 import { Designer, type DesignerMode } from '@object-ui/designer';
 import type { SchemaNode } from '@object-ui/core';
 

examples/designer-modes/src/main.tsx

@@ -1,10 +1,10 @@
-import React from 'react';
-import ReactDOM from 'react-dom/client';
+import { StrictMode } from 'react';
+import { createRoot } from 'react-dom/client';
 import App from './App';
 import './index.css';
 
-ReactDOM.createRoot(document.getElementById('root')!).render(
-  <React.StrictMode>
+createRoot(document.getElementById('root')!).render(
+  <StrictMode>
     <App />
-  </React.StrictMode>,
+  </StrictMode>,
 );

examples/designer-modes/tsconfig.json

@@ -4,6 +4,7 @@
     "useDefineForClassFields": true,
     "lib": ["ES2020", "DOM", "DOM.Iterable"],
     "module": "ESNext",
+    "types": ["vite/client"],
     "skipLibCheck": true,
 
     /* Bundler mode */