fix(coding): reject mismatched Data Service errors

tests/unit/data-service-client.test.ts

@@ -202,6 +202,24 @@ describe('DataServiceCloudClient', () => {
     });
   });
 
+  it('rejects a known error code paired with the wrong HTTP status', async () => {
+    const client = new DataServiceCloudClient({
+      fetchImpl: vi.fn<typeof fetch>().mockResolvedValue(
+        jsonResponse({ detail: { code: 'quota_exceeded' } }, { status: 400 }),
+      ),
+      getAccessToken: vi.fn().mockResolvedValue('access-token'),
+    });
+
+    const result = await client.inspect(projectId);
+
+    expect(result).toMatchObject({
+      success: false,
+      status: 502,
+      code: 'upstream_invalid_response',
+      data: null,
+    });
+  });
+
   it('normalizes malformed client errors and all upstream 5xx responses safely', async () => {
     const fetchImpl = vi.fn<typeof fetch>()
       .mockResolvedValueOnce(new Response(null, { status: 404 }))