收口入口壳加载提示面板

迁移平台入口壳纯 Suspense fallback 到 PlatformSubpanel

保留 fallback 居中布局和提示文案局部内边距

更新 PlatformUiKit 文档和 Hermes 决策记录

src/components/platform-entry/PlatformEntryFlowShellImpl.tsx

@@ -365,6 +365,7 @@ import type { CustomWorldProfile } from '../../types';
 import { useAuthUi } from '../auth/AuthUiContext';
 import { PlatformActionButton } from '../common/PlatformActionButton';
 import { PlatformModalCloseButton } from '../common/PlatformModalCloseButton';
+import { PlatformSubpanel } from '../common/PlatformSubpanel';
 import { PublishShareModal } from '../common/PublishShareModal';
 import type { PublishShareModalPayload } from '../common/publishShareModalModel';
 import { UnifiedConfirmDialog } from '../common/UnifiedConfirmDialog';
@@ -1350,9 +1351,13 @@ const PuzzleRuntimeShell = lazy(async () => {
 function LazyPanelFallback({ label }: { label: string }) {
   return (
     <div className="flex h-full min-h-0 items-center justify-center">
-      <div className="platform-subpanel rounded-2xl px-5 py-4 text-sm text-[var(--platform-text-base)]">
+      <PlatformSubpanel
+        radius="sm"
+        padding="none"
+        className="px-5 py-4 text-sm text-[var(--platform-text-base)]"
+      >
         {label}
-      </div>
+      </PlatformSubpanel>
     </div>
   );
 }