feat(codegen): P 层闭环 —— 模板生成页面 + 画廊生成面板

- src/codegen.ts:PageDeclaration → definePage 源码(漂亮缩进,语法合法)
- src/render.ts:导出 generatePageSource/starterPageFrom;画廊受控 selected/onSelect
- playground generator.tsx:选布局→填标题→生成→复制/保存到 pages/
- vite 中间件 /__vr-save:浏览器 POST 落盘 pages/(HMR 生效)
- 验证:codegen 产物通过工程 tsc;保存中间件落盘成功;画廊 UI headless 通过

examples/playground/scripts/gen-and-save.ts

@@ -0,0 +1,38 @@
+/**
+ * 用 codegen 生成真实页面源码,写入 pages/,验证产物可被工程编译
+ * 不依赖 React/tsx 注册 —— 用轻量模拟注册表
+ * 运行:node --experimental-strip-types scripts/gen-and-save.ts
+ */
+import { createRegistry } from 'vibe-registry'
+import { generatePageSource, starterPageFrom } from 'vibe-registry/render'
+import { writeFileSync, mkdirSync } from 'node:fs'
+import { join, dirname } from 'node:path'
+import { fileURLToPath } from 'node:url'
+
+const reg = createRegistry()
+reg.registerLayout({
+  kind: 'layout',
+  id: 'admin',
+  slots: ['sidebar', 'header', 'content', 'footer'],
+  description: 't',
+  preview: {
+    title: 'Admin',
+    demoBlocks: [{ slot: 'content', widget: 'data-table', props: {} }],
+  },
+})
+reg.registerWidget({ kind: 'widget', id: 'data-table', description: 't' })
+
+const page = starterPageFrom('admin', reg, '商品管理')
+const src = generatePageSource(page, {
+  products: [
+    { id: 'P01', name: '键盘', price: 299, stock: 42 },
+    { id: 'P02', name: '鼠标', price: 99, stock: 120 },
+  ],
+})
+
+const out = join(dirname(fileURLToPath(import.meta.url)), '..', 'pages', 'page-products.tsx')
+mkdirSync(dirname(out), { recursive: true })
+writeFileSync(out, src, 'utf8')
+console.log('已生成:', out)
+console.log('--- 代码(前 26 行)---')
+console.log(src.split('\n').slice(0, 26).join('\n'))