fix(runtime): replace broken React UMD vendor + unblock JSX previews

The shipped `packages/runtime/vendor/{react,react-dom}.umd.js` were broken
builds containing `if (n) let g = !0;` — invalid JS that V8 rejects with
"Lexical declaration cannot appear in a single-statement context". Every
JSX-era design therefore failed to execute inside the preview iframe:
React never defined `window.ReactDOM`, Babel then raised
`ReferenceError: ReactDOM is not defined`, and the hub thumbnails + main
PreviewPane showed as blank / "brokenJsx".

- Replace vendor with clean React 18.3.1 production UMDs from unpkg
  (react 10.7 KB, react-dom 131.8 KB).
- Scope DesignCardPreview's `transform: scale` to a wrapper div so
  Chromium doesn't defer script scheduling when the iframe itself has a
  heavy transform + tiny post-transform visible area.
- Add the missing i18n keys `preview.error.brokenJsx` /
  `preview.error.undefinedRef` (zh-CN + en) so CanvasErrorBar surfaces
  a readable message instead of the dev `⟦key⟧` fallback.

Author: hqhq1025

apps/desktop/src/renderer/src/views/hub/DesignCardPreview.tsx

@@ -180,18 +180,28 @@ export function DesignCardPreview({ design }: DesignCardPreviewProps) {
   return (
     <div ref={rootRef} className="absolute inset-0 overflow-hidden bg-white">
       {srcDoc ? (
-        <iframe
-          title={design.name}
-          srcDoc={srcDoc}
-          sandbox={isJsx ? 'allow-scripts' : ''}
-          className="pointer-events-none border-0"
+        // Scale wrapper → iframe strategy: Chromium may defer script execution
+        // for iframes with a direct CSS `transform: scale(...)` when the
+        // post-transform visible size is tiny (hub thumbnails post-scale look
+        // like ~280x211). Putting transform on a PARENT and letting the iframe
+        // keep its natural 1280x960 matches PreviewPane's layout and lets the
+        // renderer treat the iframe as full-size for execution scheduling.
+        <div
           style={{
             width: '1280px',
             height: '960px',
             transform: `scale(${scale})`,
             transformOrigin: 'top left',
           }}
-        />
+        >
+          <iframe
+            title={design.name}
+            srcDoc={srcDoc}
+            sandbox={isJsx ? 'allow-scripts' : ''}
+            className="pointer-events-none border-0"
+            style={{ width: '1280px', height: '960px' }}
+          />
+        </div>
       ) : failed ? (
         <div className="absolute inset-0 flex flex-col items-center justify-center gap-[var(--space-2)] bg-[var(--color-background-secondary)] text-[var(--color-text-muted)]">
           <Plus className="w-5 h-5 opacity-40" strokeWidth={1.5} aria-hidden />

packages/i18n/src/locales/en.json

@@ -70,6 +70,10 @@
     "commentMode": "Comment mode",
     "commentModeHint": "Click any element to comment",
     "runtimeError": "Preview runtime error",
+    "error": {
+      "brokenJsx": "This design has a syntax error, likely an incomplete early save. Regenerate or edit to fix.",
+      "undefinedRef": "The design references an undefined variable or component. Likely a mid-run abort — try regenerating."
+    },
     "dismissErrors": "Dismiss preview errors",
     "zoom": "Zoom"
   },

packages/i18n/src/locales/zh-CN.json

@@ -72,6 +72,10 @@
     "commentMode": "评论模式",
     "commentModeHint": "点击任意元素留评",
     "runtimeError": "预览运行时错误",
+    "error": {
+      "brokenJsx": "此设计的代码有语法错误，可能是早期版本保存的不完整内容。重新生成或编辑修复即可。",
+      "undefinedRef": "设计引用了未定义的变量或组件。可能是生成中途中断——尝试重新生成。"
+    },
     "dismissErrors": "关闭预览错误",
     "zoom": "缩放"
   },