fix(plaza): use hero-generated thumbnails and portal cover URLs

Plaza posts now resolve cover_url to /u/{slug}/pages/{urlSlug}.thumbnail.png
instead of MindSpace workspace paths that fail on plaza.tkmind.cn. Public-html
and chat quick-plaza flows regenerate workspace thumbnails with force:true
after hero images are on disk so feed cards embed the generated art.

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

mindspace-chat-plaza.mjs

@@ -255,21 +255,43 @@ export async function quickPlazaFromChat({
   mindSpacePages,
   mindSpacePublications,
   plazaPosts,
+  ensureWorkspaceHtmlThumbnail,
+  publishDir,
 }) {
   if (!mindSpacePages || !mindSpacePublications || !plazaPosts) {
     throw Object.assign(new Error('Plaza 或 MindSpace 未启用'), { code: 'plaza_unavailable' });
   }
 
-  const { analysis } = bundle;
+  const { analysis, resolvedHtml } = bundle;
   const page = await ensureChatPageForPlaza({
     userId: user.id,
     bundle,
     mindSpacePages,
+    ensureWorkspaceHtmlThumbnail,
     publishDir,
     body,
-    skipThumbnail: true,
+    skipThumbnail: !ensureWorkspaceHtmlThumbnail || !publishDir,
   });
 
+  if (
+    analysis.contentMode === 'static_html' &&
+    analysis.relativePath &&
+    resolvedHtml?.content &&
+    ensureWorkspaceHtmlThumbnail &&
+    publishDir
+  ) {
+    await ensureWorkspaceHtmlThumbnail(
+      publishDir,
+      analysis.relativePath,
+      resolvedHtml.content,
+      {
+        title: page.title,
+        subtitle: page.summary,
+        force: true,
+      },
+    ).catch(() => {});
+  }
+
   if (analysis.contentMode === 'static_html' && analysis.relativePath) {
     await assertWorkspacePathNotAlreadyOnPlaza({
       userId: user.id,
@@ -372,6 +394,8 @@ export async function quickPlazaFromPublicHtml({
   mindSpacePublications,
   plazaPosts,
   readWorkspaceHtml,
+  ensureWorkspaceHtmlThumbnail,
+  publishDir,
 }) {
   if (!mindSpacePages || !mindSpacePublications || !plazaPosts) {
     throw Object.assign(new Error('Plaza 或 MindSpace 未启用'), { code: 'plaza_unavailable' });
@@ -396,11 +420,19 @@ export async function quickPlazaFromPublicHtml({
     relativePath: normalized,
   });
 
+  const title = titleFromPublicHtml(content, normalized);
+  if (ensureWorkspaceHtmlThumbnail && publishDir) {
+    await ensureWorkspaceHtmlThumbnail(publishDir, normalized, content, {
+      title,
+      force: true,
+    }).catch(() => {});
+  }
+
   const page = await ensureWorkspaceHtmlPageForPlaza({
     userId: user.id,
     relativePath: normalized,
     content,
-    title: titleFromPublicHtml(content, normalized),
+    title,
     mindSpacePages,
   });