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/index.css

@@ -566,3 +566,67 @@ html, body, #root {
 .gm-check-star { color: var(--yellow); }
 
 .gm-complete-actions { display: flex; gap: 8px; justify-content: center; }
+
+/* World stars counter */
+.gm-world-stars {
+  display: flex; align-items: center; gap: 4px;
+  font-size: 14px; color: var(--text2);
+  background: var(--surface); border-radius: 12px; padding: 4px 10px;
+}
+.gm-world-stars .star.filled { color: var(--yellow); }
+
+/* ===== Zoom Controls (Google Maps style) ===== */
+.zoom-controls {
+  position: absolute;
+  top: 12px;
+  right: 12px;
+  z-index: 50;
+  display: flex;
+  flex-direction: column;
+  background: var(--surface);
+  border: 1px solid var(--border);
+  border-radius: 8px;
+  overflow: hidden;
+  box-shadow: 0 2px 8px rgba(0,0,0,0.4);
+}
+.zoom-btn {
+  width: 36px;
+  height: 32px;
+  display: flex;
+  align-items: center;
+  justify-content: center;
+  background: transparent;
+  color: var(--text);
+  border: none;
+  cursor: pointer;
+  font-size: 18px;
+  font-weight: 600;
+  transition: background 0.15s;
+}
+.zoom-btn:hover {
+  background: var(--surface2);
+}
+.zoom-btn:active {
+  background: var(--border);
+}
+.zoom-btn.zoom-label {
+  font-size: 10px;
+  font-weight: 500;
+  color: var(--text2);
+  border-top: 1px solid var(--border);
+  border-bottom: 1px solid var(--border);
+  height: 26px;
+  width: 36px;
+}
+
+/* Zoom positioning inside puzzle canvas */
+.gm-puzzle-canvas-wrap .zoom-controls {
+  top: 12px;
+  right: 12px;
+}
+
+/* Position zoom inside sandbox main-area (offset for palette sidebar) */
+.main-area .zoom-controls {
+  top: 12px;
+  right: 220px;
+}