Several worlds: a Worlds list with load, rename and delete; old save migrates to World 1

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

src/ui/state.js

@@ -42,7 +42,7 @@ const GAME = {
   brush: [3, 2, 0, 0, 0], collect: loadCollect(), tipsOpen: new Set(), cards: [], vacFilter: 0, vacLocked: false, rmbConsumed: false, rmbSeen: new Set(), lookHold: { x: 0, y: 0 },
   paste: false, selDrag: null, rmbRec: null, dragDir: -1, replaceShown: false, clip: null, drag: null, aim: { x: 0, y: 0 }, mouse: { x: 0, y: 0, in: false },
   lmb: false, rmb: false, blowMix: false, drillW: 1, drillTune: 0, lastDug: 0, padRun: 0, status: '', statusKind: 'err', statusT: 0, usingPad: false, padAim: { x: 12, y: 0 },
-  lastAutosave: 0, playTime: 0, lastHud: 0, worldName: '',
+  lastAutosave: 0, playTime: 0, lastHud: 0, worldId: '', worldName: '',
 };
 const keys = new Set();
 let hudDirty = true;