优化预览变换回退分配

复用空的预览变换映射，避免节点递归渲染重复分配

apps/ai-game-creator-shell/src/view/ui-editor/components/preview/UiTreeRenderer.tsx

@@ -71,6 +71,11 @@ const RESIZE_HANDLES: ReadonlyArray<{
   { id: 'w', left: '0%', top: '50%', cursor: 'ew-resize' },
 ];
 
+const EMPTY_PREVIEW_TRANSFORMS: ReadonlyMap<
+  NodeId,
+  UiNode['layout']['transform']
+> = new Map();
+
 function RenderNode({
   node,
   isRoot,
@@ -96,7 +101,7 @@ function RenderNode({
   isRoot?: boolean;
   parentContainer?: UiNode['layout']['container'];
 }) {
-  const activePreviewTransforms = previewTransforms ?? new Map();
+  const activePreviewTransforms = previewTransforms ?? EMPTY_PREVIEW_TRANSFORMS;
   if (hiddenNodeIds.has(node.id)) return null;
   const layout = activePreviewTransforms.has(node.id)
     ? { ...node.layout, transform: activePreviewTransforms.get(node.id)! }