Fix OA workspace cover thumbnails and add space chat new session.

Resolve mindspace-cover images from workspace directories when generating feed thumbnails, refresh stale SVGs missing embedded photos, and disable thumbnail API caching so fixes take effect immediately. Also add a new session control to the space chat panel, including on mobile.

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

mindspace-pages.mjs

@@ -10,6 +10,7 @@ import {
   pageThumbnailKey,
   writeThumbnail,
   bufferToImageDataUri,
+  resolveWorkspaceHtmlContentBaseDir,
 } from './mindspace-thumbnails.mjs';
 import { resolvePublishDir } from './user-publish.mjs';
 import { ensureWorkspaceHtmlThumbnail, workspaceThumbnailRelativePath } from './mindspace-workspace-thumbnails.mjs';
@@ -951,6 +952,10 @@ export function createPageService(pool, options = {}) {
       title,
       subtitle: summary || `草稿 v${asNumber(ctx.row.version_no)}`,
       contentStorageKey: ctx.row.storage_key,
+      contentBaseDir: resolveWorkspaceHtmlContentBaseDir(
+        ctx.workspacePublishDir,
+        ctx.workspaceHtmlRelativePath,
+      ),
       force: true,
       ...metaOverrides,
     };