feat: add mock batch submit endpoint

README.md

@@ -56,6 +56,18 @@ The popup dev panel is controlled by `enableDevAuthPanel`.
 6. Click `测试受保护接口`
 7. Confirm the popup shows JSON containing `"source": "mock-protected-api"` and `"message": "authorized"`
 
+## Batch Submit Mock Test
+
+1. Run `npm run mock:protected-api`
+2. Run `npm run build`
+3. Reload the unpacked extension from `dist/`
+4. Open `https://xingtu.cn/ad/creator/market`
+5. Choose an export range in the plugin toolbar
+6. Click `提交批次`
+7. Enter a batch name in the browser prompt
+8. Confirm the toolbar shows `批次提交成功`
+9. Confirm the mock batch response accepts the payload and reports the submitted `batchId`
+
 ## Market Auth Gate
 
 When the market page is opened without a valid auth state, the content script renders