fix(mindspace-public): 公开页区分作者与访客视图 + 图片加载自动重试

工作区直链 /MindSpace/<userId>/public/*.html 此前对所有人（含匿名访客、
转发链接收到的其他登录用户）展示完全相同的悬浮操作按钮，导致非作者也能
看到"发布 Plaza"入口——而 Plaza 发布会把内容归属到操作者自己的账号下，
必须只对作者开放。

- server.mjs: serveUserPublishFile 用现有 session/cookie 鉴权判断访问者是
  否等于 URL 中的 ownerKey，结果透传给 sendPublishFile；该响应内容因人
  而异，显式加 Cache-Control: private, no-store（原来未设置任何缓存头）
- mindspace-public-share-widget.mjs: injectPublicFileShareButton 新增
  isOwner 参数（默认 true 保持兼容），非作者时隐藏"发布 Plaza"按钮与确认
  弹窗，"保存长图"/"公开分享"对所有访客保留
- mindspace-public-delivery.mjs: 透传 isOwner，并注入图片重试脚本
- mindspace-public-image-retry.mjs（新增）: 页面级 onerror 之前用捕获阶段
  监听拦截 mindspace 资产图片的加载失败，带退避自动重试 3 次，避免刚生成
  页面时的资产物化竞态被"永久占位符"放大成显示故障

本地起服务用 owner / 非 owner 已登录用户 / 匿名访客三种身份实测验证。

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

server.mjs

@@ -5756,7 +5756,7 @@ async function ensurePublicHtmlPrivateAssetsMaterialized(filePath, html) {
   return result.changed ? result.html : html;
 }
 
-async function sendPublishFile(req, res, filePath) {
+async function sendPublishFile(req, res, filePath, { isOwner = true } = {}) {
   if (!filePath.toLowerCase().endsWith('.html')) {
     res.sendFile(filePath, (err) => {
       if (err && !res.headersSent) res.status(404).json({ message: '文件不存在' });
@@ -5788,6 +5788,7 @@ async function sendPublishFile(req, res, filePath) {
   const decorated = decorateMindSpacePublishedHtml({
     html,
     embed,
+    isOwner,
     context,
     htmlFilePath: filePath,
     userAgent: req.get('user-agent') || '',
@@ -5804,6 +5805,10 @@ async function sendPublishFile(req, res, filePath) {
   }
   res.set('Content-Security-Policy', decorated.csp);
   res.set('Content-Type', 'text/html; charset=utf-8');
+  // REGRESSION GUARD: mindspace-public-owner-vs-visitor — this HTML now varies by viewer
+  // (owner sees the Plaza entry, visitors don't), so it must never be cached/shared across
+  // sessions. There is no CDN/proxy_cache in front of this route today; keep it that way.
+  res.set('Cache-Control', 'private, no-store');
   res.send(html);
 }
 
@@ -5861,7 +5866,17 @@ async function serveUserPublishFile(req, res, next) {
     }
   }
 
-  await sendPublishFile(req, res, resolvedPath);
+  // REGRESSION GUARD: mindspace-public-owner-vs-visitor — this workspace URL is the one the
+  // agent hands back in chat and is reachable by anyone (no login required). Only the logged-in
+  // author (viewer.id === ownerKey) may see the "发布 Plaza" entry; everyone else is a visitor.
+  const viewer = req.userSession && userAuth
+    ? await userAuth.getMe(req.userToken).catch(() => null)
+    : null;
+  const isOwner = Boolean(
+    viewer?.id && result.ownerKey && String(viewer.id).toLowerCase() === String(result.ownerKey).toLowerCase(),
+  );
+
+  await sendPublishFile(req, res, resolvedPath, { isOwner });
 }
 
 app.use('/temp', (req, res) => {