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-server-adapter-contract.mjs

@@ -31,6 +31,7 @@ export const MINDSPACE_SERVER_ADAPTER_BINDINGS = Object.freeze({
     'findPageByRelativePath',
     'findPageBySourceAsset',
     'findPageBySourceMessage',
+    'findPlazaContextByWorkspacePath',
     'getDeletePreview',
     'getPage',
     'listPages',
@@ -56,6 +57,7 @@ export const MINDSPACE_SERVER_ADAPTER_BINDINGS = Object.freeze({
     'getStats',
     'offline',
     'publish',
+    'refreshOnlinePublicationHtml',
     'resolvePrivateLink',
     'resolvePublic',
     'updatePublicationStatus',