feat(render): M2 — React 渲染内核 + 布局画廊(playground)

- core 新增 render 子路径(vibe-registry/render):PageView + WidgetView + LayoutGallery
- layout 注册项支持 render 实现;缺省兜底 DefaultLayout
- widget 注册项 component 挂真实 React 组件
- PageBlockDecl 增加 slot 字段(块落在布局哪个槽位)
- playground:admin 布局真实骨架 + 组件 + 订单页,dev 预览 + 生产构建通过
- 全量回归:core/qa-orchestrator/playground typecheck 全绿

examples/playground/package.json

@@ -0,0 +1,24 @@
+{
+  "name": "vibe-playground",
+  "version": "0.0.1",
+  "private": true,
+  "type": "module",
+  "description": "vibe-registry 渲染验证 playground:画廊 + 真实 React 渲染",
+  "scripts": {
+    "dev": "vite",
+    "build": "tsc --noEmit && vite build",
+    "typecheck": "tsc --noEmit"
+  },
+  "dependencies": {
+    "react": "^18.3.0",
+    "react-dom": "^18.3.0",
+    "vibe-registry": "workspace:*"
+  },
+  "devDependencies": {
+    "@types/react": "^18.3.0",
+    "@types/react-dom": "^18.3.0",
+    "@vitejs/plugin-react": "^4.3.0",
+    "typescript": "^5.8.0",
+    "vite": "^6.0.0"
+  }
+}