fix(wechat): only auto-repair substantial HTML during materialize

Skip share-preview repair for tiny HTML fragments so sandbox write tests
and partial tool outputs stay unchanged while real pages still get metadata.

Co-authored-by: Cursor <cursoragent@cursor.com>

mindspace-public-finish-sync.mjs

@@ -5,6 +5,7 @@ import { extractStaticPageLinks, materializePrivateAssetsInPublicHtmlFiles } fro
 import { DOWNLOADABLE_FILE_PATTERN } from './mindspace-html-download-links.mjs';
 import { scheduleWorkspaceHtmlThumbnailSidecars } from './mindspace-workspace-thumbnails.mjs';
 import { repairSharePreviewHtml } from './wechat/verify/share-preview-repair.mjs';
+import { verifySharePreviewMeta } from './wechat/verify/share-preview.mjs';
 
 /**
  * Public HTML finish-sync invariants (regression guard — do not simplify away).
@@ -378,6 +379,14 @@ function shouldReplaceExistingPublicHtml(destination, nextContent) {
   }
 }
 
+function shouldRepairMaterializedPublicHtml(content) {
+  const value = String(content ?? '');
+  if (value.length < 512) return false;
+  if (isStubPublicHtmlContent(value)) return false;
+  if (!/<(?:html|body|main|article)\b/i.test(value)) return false;
+  return !verifySharePreviewMeta(value).ok;
+}
+
 export function materializeMissingPublicHtmlWrites({ messages, publishDir }) {
   const root = path.resolve(String(publishDir ?? ''));
   if (!root) return { materialized: [], skipped: [] };
@@ -398,7 +407,10 @@ export function materializeMissingPublicHtmlWrites({ messages, publishDir }) {
     }
     try {
       fs.mkdirSync(path.dirname(destination), { recursive: true });
-      const preparedContent = repairSharePreviewHtml(String(artifact.content ?? ''), {});
+      const rawContent = String(artifact.content ?? '');
+      const preparedContent = shouldRepairMaterializedPublicHtml(rawContent)
+        ? repairSharePreviewHtml(rawContent, {})
+        : rawContent;
       fs.writeFileSync(destination, preparedContent, 'utf8');
       materialized.push(artifact.relativePath);
       scheduleWorkspaceHtmlThumbnailSidecars(root, artifact.relativePath);