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/world/gameMode.js

@@ -0,0 +1,173 @@
+// gameMode.js - Central coordinator: switches between World and Workshop modes
+import { worldState, setPlayerPosition, warpToMap, solvePuzzle, isPuzzleSolved } from './worldState.js';
+import { initWorldRenderer, startWorldLoop, stopWorldLoop } from './worldRenderer.js';
+import { initWorldInput, destroyWorldInput, setInteractionHandler } from './worldInput.js';
+import { getMap } from './maps.js';
+
+// Circuit editor stop function (to stop its render loop when switching modes)
+import { stopCircuitLoop } from '../renderer.js';
+
+// Circuit editor modules (registered from app.js to avoid circular deps)
+let circuitEditorInit = null;
+let circuitEditorDestroy = null;
+
+let currentMode = 'none'; // 'world' | 'workshop'
+
+/**
+ * Register the circuit editor's init/destroy functions.
+ * Called from app.js so we don't create circular imports.
+ */
+export function registerCircuitEditor(initFn, destroyFn) {
+    circuitEditorInit = initFn;
+    circuitEditorDestroy = destroyFn;
+}
+
+/**
+ * Boot the game — start in world mode
+ */
+export function startGame() {
+    // Set spawn
+    const map = getMap(worldState.currentMap);
+    if (map && map.spawn) {
+        setPlayerPosition(map.spawn.x, map.spawn.y);
+    }
+
+    // Wire up interaction handler
+    setInteractionHandler(handleInteraction);
+
+    // Enter world mode
+    enterWorldMode();
+}
+
+// ==================== Mode switching ====================
+
+export function enterWorldMode() {
+    if (currentMode === 'world') return;
+
+    // Tear down workshop if active
+    if (currentMode === 'workshop') {
+        stopCircuitLoop();
+        if (circuitEditorDestroy) circuitEditorDestroy();
+        hideWorkshopUI();
+    }
+
+    currentMode = 'world';
+    worldState.mode = 'world';
+
+    showWorldUI();
+    initWorldRenderer();
+    initWorldInput();
+    startWorldLoop();
+
+    console.log('[gameMode] entered world mode');
+}
+
+export function enterWorkshopMode() {
+    if (currentMode === 'workshop') return;
+
+    // Tear down world
+    if (currentMode === 'world') {
+        stopWorldLoop();
+        destroyWorldInput();
+        hideWorldUI();
+    }
+
+    currentMode = 'workshop';
+    worldState.mode = 'workshop';
+
+    showWorkshopUI();
+    if (circuitEditorInit) circuitEditorInit();
+
+    console.log('[gameMode] entered workshop mode');
+}
+
+export function getCurrentMode() { return currentMode; }
+
+// ==================== Interaction handler ====================
+
+function handleInteraction(event) {
+    switch (event.type) {
+        case 'enterWorkshop':
+            enterWorkshopMode();
+            break;
+
+        case 'puzzleDoor': {
+            const inter = event.data;
+            if (isPuzzleSolved(inter.puzzleId)) {
+                // Already solved — could open door, show message, etc.
+                return;
+            }
+            // For now, show a hint dialog. Later: open puzzle UI
+            worldState.dialog = {
+                lines: [
+                    'This door requires a logic circuit to open.',
+                    `Required output pattern: [${inter.requiredOutputs.join(', ')}]`,
+                    'Craft a component in your Workshop (TAB)!'
+                ],
+                currentLine: 0,
+                speakerName: 'System'
+            };
+            worldState.mode = 'dialog';
+            break;
+        }
+
+        case 'mapExit': {
+            const { targetMap, targetX, targetY } = event.data;
+            warpToMap(targetMap, targetX, targetY);
+            console.log(`[gameMode] warped to ${targetMap} (${targetX}, ${targetY})`);
+            break;
+        }
+
+        case 'openInventory':
+            // TODO: inventory UI
+            console.log('[gameMode] inventory:', worldState.inventory);
+            break;
+    }
+}
+
+// ==================== UI visibility ====================
+
+function showWorldUI() {
+    // Hide workshop-specific elements
+    const toolbar = document.getElementById('toolbar');
+    const wavePanel = document.getElementById('waveform-panel');
+    const canvas = document.getElementById('canvas');
+
+    if (toolbar) toolbar.style.display = 'none';
+    if (wavePanel) wavePanel.style.display = 'none';
+    if (canvas) {
+        canvas.style.top = '0';
+        canvas.style.cursor = 'default';
+    }
+
+    // Show back-to-world button (hidden since we're IN world)
+    const backBtn = document.getElementById('back-to-world-btn');
+    if (backBtn) backBtn.style.display = 'none';
+}
+
+function hideWorldUI() {
+    // Nothing special to hide — canvas stays
+}
+
+function showWorkshopUI() {
+    const toolbar = document.getElementById('toolbar');
+    const canvas = document.getElementById('canvas');
+
+    if (toolbar) toolbar.style.display = 'flex';
+    if (canvas) {
+        canvas.style.top = '56px';
+        canvas.style.cursor = 'default';
+    }
+
+    // Show back-to-world button
+    const backBtn = document.getElementById('back-to-world-btn');
+    if (backBtn) backBtn.style.display = 'flex';
+}
+
+function hideWorkshopUI() {
+    const toolbar = document.getElementById('toolbar');
+    if (toolbar) toolbar.style.display = 'none';
+
+    const backBtn = document.getElementById('back-to-world-btn');
+    if (backBtn) backBtn.style.display = 'none';
+}