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>

package.json

@@ -39,6 +39,8 @@
     "build:mindspace-service-runtime": "node scripts/build-mindspace-service-runtime.mjs",
     "check:mindspace-public-links": "node scripts/check-mindspace-public-links.mjs --downloads-only",
     "check:mindspace-public-links:all": "node scripts/check-mindspace-public-links.mjs --all-links",
+    "check:mindspace-cover": "node scripts/check-mindspace-cover.mjs",
+    "demo:thumbnails": "node scripts/thumbnail-preview-demo.mjs",
     "check:conversation-package-manifest": "node scripts/check-conversation-package-manifest.mjs",
     "check:memory-v2": "node scripts/check-memory-v2-health.mjs",
     "canary:memory-v2-app": "node scripts/check-memory-v2-app-canary.mjs",