fix: display canonical API failure labels in the grading page

frontend/tests/batches.spec.ts

@@ -140,12 +140,14 @@ test('failed scoring shows the network error and retry guidance on the page', as
   await page.route('**/api/projects/11/scores?*', route => route.fulfill({ json: {
     student_no: '9000000001', name: '学生甲', topic: '项目', totals: { overall: null }, facts: {},
     rows: [{ criterion: { criterion_id: 'stage1.problem', category: 'stage1', name: '需求分析', max_score: 25 },
-      status: 'failed', error: 'ConnectError：无法连接模型端点，请检查 Docker 网络、DNS 或代理',
+      status: 'failed', status_label: '模型连接失败',
+      error: '模型请求或JSON校验失败（ConnectError：无法连接模型端点，请检查 Docker 网络、DNS 或代理），已重试2次',
       evidence: [], missing_evidence: [], evidence_gaps: [] }],
   } }));
   await page.goto('/?page=scores&batch_id=71&project_id=11');
   await expect(page.getByText('当前项目有 1 项评分失败', { exact: true })).toBeVisible();
   await expect(page.getByText(/ConnectError：无法连接模型端点/)).toBeVisible();
+  await expect(page.getByText('模型连接失败', { exact: true })).toBeVisible();
   await expect(page.getByText(/已经成功的评分和教师复核会保留/)).toBeVisible();
 });