feat: add Pokemon-style world mode with workshop integration

Two-mode game: explore a tile-based cyberpunk world, then enter
Workshop mode (the existing circuit editor) to craft components.

New modules (js/world/):
- sprites.js: programmatic pixel-art renderer (16x16 tiles, 3x scale)
- maps.js: tile-based map definitions (lab + town)
- worldState.js: player position, inventory, dialog, puzzle state
- worldRenderer.js: camera-following world renderer on shared canvas
- worldInput.js: WASD movement, E interaction, dialog system
- gameMode.js: central mode switcher (world ↔ workshop)

Changes to existing code:
- app.js: boots into world mode, registers circuit editor for workshop
- renderer.js: circuit draw loop now stoppable (start/stopCircuitLoop)
- index.html: added "Back to World" button for workshop mode

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

js/app.js

@@ -1,22 +1,40 @@
-// Entry point — initializes all modules
-import { initRenderer } from './renderer.js';
+// Entry point — initializes game (world + workshop modes)
+import { initRenderer, resize } from './renderer.js';
 import { initEvents } from './events.js';
 import { initPuzzleUI } from './puzzleUI.js';
 import { loadFromStorage, startAutoSave } from './saveLoad.js';
 import { updateComponentButtons } from './components.js';
 import { evaluateAll } from './gates.js';
+import { startGame, registerCircuitEditor, enterWorldMode } from './world/gameMode.js';
 
 document.addEventListener('DOMContentLoaded', () => {
-    initRenderer();
-    initEvents();
-    initPuzzleUI();
+    // Register circuit editor init/destroy so gameMode can switch to workshop
+    registerCircuitEditor(
+        // init workshop
+        () => {
+            initRenderer();
+            initEvents();
+            initPuzzleUI();
+            if (loadFromStorage()) {
+                updateComponentButtons();
+                evaluateAll();
+            }
+            startAutoSave(3000);
+        },
+        // destroy workshop (cleanup when switching back to world)
+        () => {
+            // Auto-save is fine to leave running
+        }
+    );
 
-    // Restore previous session from localStorage
-    if (loadFromStorage()) {
-        updateComponentButtons();
-        evaluateAll();
+    // Add back-to-world button handler
+    const backBtn = document.getElementById('back-to-world-btn');
+    if (backBtn) {
+        backBtn.addEventListener('click', () => {
+            enterWorldMode();
+        });
     }
 
-    // Auto-save every 3 seconds + on page unload
-    startAutoSave(3000);
+    // Start the game in world mode
+    startGame();
 });