fix(platform): keep dashboard metrics on preview failures

vehicle-data-platform/apps/web/src/test/App.test.tsx

@@ -135,6 +135,79 @@ test('dashboard renders vehicle service summary metrics', async () => {
   expect(fetchMock).toHaveBeenCalledWith('/api/vehicle-service/summary', undefined);
 });
 
+test('dashboard keeps core vehicle service metrics when preview requests fail', async () => {
+  window.history.replaceState(null, '', '/#/dashboard');
+  vi.spyOn(globalThis, 'fetch').mockImplementation(async (input) => {
+    const path = String(input);
+    if (path.includes('/api/dashboard/summary')) {
+      return {
+        ok: true,
+        json: async () => ({
+          data: {
+            onlineVehicles: 3,
+            activeToday: 4,
+            frameToday: 1286320,
+            issueVehicles: 7,
+            kafkaLag: 0,
+            protocols: [],
+            serviceStatuses: [],
+            linkHealth: []
+          },
+          traceId: 'trace-test',
+          timestamp: 1783094400000
+        })
+      } as Response;
+    }
+    if (path.includes('/api/vehicle-service/summary')) {
+      return {
+        ok: true,
+        json: async () => ({
+          data: {
+            totalVehicles: 1033,
+            boundVehicles: 1024,
+            onlineVehicles: 208,
+            singleSourceVehicles: 391,
+            multiSourceVehicles: 181,
+            noDataVehicles: 461,
+            identityRequiredVehicles: 9,
+            serviceStatuses: [],
+            protocols: [],
+            missingSources: []
+          },
+          traceId: 'trace-test',
+          timestamp: 1783094400000
+        })
+      } as Response;
+    }
+    if (path.includes('/api/quality/issues')) {
+      return {
+        ok: false,
+        status: 500,
+        json: async () => ({
+          error: { message: '质量预览失败', detail: 'TDengine timeout' },
+          traceId: 'trace-quality',
+          timestamp: 1783094400000
+        })
+      } as Response;
+    }
+    return {
+      ok: true,
+      json: async () => ({
+        data: { items: [], total: 0, limit: 8, offset: 0 },
+        traceId: 'trace-test',
+        timestamp: 1783094400000
+      })
+    } as Response;
+  });
+
+  render(<App />);
+
+  expect(await screen.findByText('总车辆')).toBeInTheDocument();
+  expect(screen.getAllByText('1,033').length).toBeGreaterThanOrEqual(1);
+  expect(screen.getByText('单源车辆')).toBeInTheDocument();
+  expect(screen.getByText('391')).toBeInTheDocument();
+});
+
 test('opens dashboard coverage from missing source distribution', async () => {
   window.history.replaceState(null, '', '/#/dashboard');
   const fetchMock = vi.spyOn(globalThis, 'fetch').mockImplementation(async (input) => {