feat: add SynthQuest game mode with World 1 (Waves) — 8 puzzle levels

Gamified synth learning inspired by Turing Complete. Progressive puzzle
system teaches oscillators, waveforms, frequency, and mixing through
hands-on module patching. Includes world map, level progression with
3-star rating, target audio playback, solution validation, and
localStorage persistence. Sandbox mode still accessible via button.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

src/main.jsx

@@ -1,6 +1,17 @@
-import React from 'react';
+import React, { useState } from 'react';
 import { createRoot } from 'react-dom/client';
 import App from './App';
+import GameApp from './game/GameApp.jsx';
 import './index.css';
 
-createRoot(document.getElementById('root')).render(<App />);
+function Root() {
+  const [mode, setMode] = useState('game'); // 'game' | 'sandbox'
+
+  if (mode === 'sandbox') {
+    return <App onSwitchToGame={() => setMode('game')} />;
+  }
+
+  return <GameApp onSwitchToSandbox={() => setMode('sandbox')} />;
+}
+
+createRoot(document.getElementById('root')).render(<Root />);