fix(studio): 笔记切换页面不刷新 + 侧边栏错误提示友好化

- WorkspaceRoutes 给 StudioNotebookDetailPage 加 key={notebookId}，切换笔记时强制重新挂载
- createSearchSpace 接口失败时解析响应体 detail 字段，直接展示服务端错误信息

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

frontend-web/src/core/studio/api.ts

@@ -46,7 +46,10 @@ export async function createSearchSpace(
     },
     body: JSON.stringify({ name, description: "", citations_enabled: true }),
   });
-  if (!res.ok) throw new Error(`创建失败：${res.status}`);
+  if (!res.ok) {
+    const body = await res.json().catch(() => null);
+    throw new Error(body?.detail || `创建失败：${res.status}`);
+  }
 }
 
 export async function uploadSourceText(