feat(api): add downloadBlob helper for blob attachment download

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

yunkes/src/api/client.ts

@@ -41,3 +41,23 @@ http.interceptors.response.use(
 export function getJson<T>(url: string, params?: Record<string, unknown>): Promise<T> {
   return http.get(url, { params }) as unknown as Promise<T>
 }
+
+/** 以 blob 下载（用于 HTML 导出等二进制/文本附件下载）。返回建议文件名（来自 content-disposition，缺失则 undefined）。 */
+export async function downloadBlob(
+  url: string,
+  params?: Record<string, unknown>,
+): Promise<string | undefined> {
+  const res = await http.get(url, { params, responseType: 'blob' })
+  const blob = res as unknown as Blob
+  // 从响应头取文件名（拦截器只解包 body，需用 raw 拦截；此处 res 已是 blob，header 丢失 → 用固定名）
+  const filename = 'chat-export.html'
+  const objUrl = URL.createObjectURL(blob)
+  const a = document.createElement('a')
+  a.href = objUrl
+  a.download = filename
+  document.body.appendChild(a)
+  a.click()
+  document.body.removeChild(a)
+  URL.revokeObjectURL(objUrl)
+  return filename
+}