feat(ui-migration): 源数据加载与校验

读取 gameabc_{Object,Layer,GroupList,Image}.json, 跳过 {} 占位槽,
校验多帧图的网格与帧数一致(不符即显式抛错, 不兜底)。
真实数据回归护栏: 991 对象 / 55 界面 / 80 组 / 439 图 / 139 多帧图。
引入 pngjs devDep 供后续切图使用(仅迁移工具, 不进框架运行时)。

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

cocoscreator_projects/package.json

@@ -11,12 +11,15 @@
     "bump-cocos": "node scripts/bump-cocos.mjs",
     "check-skin": "node scripts/check-skin.mjs",
     "build-game": "node scripts/build-game.mjs",
+    "convert-ui": "node scripts/convert-ui.mjs",
+    "verify-frames": "node scripts/verify-frames.mjs",
     "test:framework": "node scripts/run-framework-tests.mjs",
     "typecheck:framework": "tsc -p tsconfig.framework.json --noEmit"
   },
   "devDependencies": {
     "@types/node": "^26.0.1",
     "@types/ws": "^8.18.1",
+    "pngjs": "^7.0.0",
     "tsx": "^4.22.4",
     "typescript": "^6.0.3",
     "ws": "^8.21.0"