feat(mindspace): 公开页分享组件、workspace 路径与 Plaza 发布增强

- 新增 public share widget 与 workspace relative path 解析
- 增强 publications/chat-plaza 发布链路与缩略图 demo
- 补充 schema、cover 检查脚本与回归测试

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

mindspace-workspace-path.mjs

@@ -0,0 +1,29 @@
+import { normalizeWorkspaceRelativePath } from './mindspace-pages.mjs';
+
+export { normalizeWorkspaceRelativePath };
+
+export function resolvePageWorkspaceRelativePath(snapshot) {
+  if (!snapshot || typeof snapshot !== 'object') return null;
+  return normalizeWorkspaceRelativePath(snapshot.relative_path) || null;
+}
+
+export function resolveAssetWorkspaceRelativePath({
+  categoryCode = null,
+  originalFilename = null,
+  explicitPath = null,
+} = {}) {
+  const explicit = normalizeWorkspaceRelativePath(explicitPath);
+  if (explicit) return explicit;
+  const filename = String(originalFilename ?? '')
+    .replace(/\\/g, '/')
+    .replace(/^\/+/, '');
+  if (!filename) return null;
+  if (/^(?:public|oa)\//i.test(filename)) {
+    return normalizeWorkspaceRelativePath(filename);
+  }
+  const category = String(categoryCode ?? '').trim();
+  if (category === 'public' || category === 'oa') {
+    return normalizeWorkspaceRelativePath(`${category}/${filename}`);
+  }
+  return null;
+}