feat: add Worlds 2-3, patch persistence, and zoom controls

- World 2 (Filtros): 8 levels teaching filters, resonance, LFO modulation, acid bass
- World 3 (Envelopes): 8 levels teaching VCA, ADSR, pluck, tremolo, full synth lead
- Star-based world unlock system (12 stars for W2, 24 for W3)
- Level patch persistence: auto-saves player patches, restores on revisit
- Google Maps-style zoom controls (+/−/reset) in both puzzle and sandbox views
- Multi-world navigation in GameApp and WorldMap
- Target audio now supports filter chain for World 2 levels

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

src/App.jsx

@@ -174,6 +174,22 @@ export default function App({ onSwitchToGame }) {
 
   const handleContextMenu = useCallback((e) => e.preventDefault(), []);
 
+  // Zoom controls (Google Maps style)
+  const handleZoomIn = useCallback(() => {
+    state.zoom = Math.min(3, state.zoom * 1.25);
+    emit();
+  }, []);
+  const handleZoomOut = useCallback(() => {
+    state.zoom = Math.max(0.3, state.zoom / 1.25);
+    emit();
+  }, []);
+  const handleZoomReset = useCallback(() => {
+    state.zoom = 1;
+    state.camX = 0;
+    state.camY = 0;
+    emit();
+  }, []);
+
   const handleToggleAudio = async () => {
     if (state.isRunning) {
       stopAudio();
@@ -279,6 +295,15 @@ export default function App({ onSwitchToGame }) {
           </div>
         </div>
 
+        {/* Zoom controls — top right of canvas */}
+        <div className="zoom-controls">
+          <button className="zoom-btn" onClick={handleZoomIn} title="Zoom in">+</button>
+          <button className="zoom-btn zoom-label" onClick={handleZoomReset} title="Reset zoom">
+            {(state.zoom * 100).toFixed(0)}%
+          </button>
+          <button className="zoom-btn" onClick={handleZoomOut} title="Zoom out">−</button>
+        </div>
+
         {/* Module palette */}
         <ModulePalette onAddModule={handleAddModule} />
       </div>