test: keep webui CI hermetic offline

tests/test_webui_queue_dashboard.py

@@ -206,8 +206,9 @@ class TestQueueRoutes(unittest.TestCase):
         self.assertEqual(data["pagination"]["issues"]["returned_count"], 3)
 
     def test_queue_fail_closed_without_credentials(self):
-        with mock.patch("webui.queue_loader.get_auth_header", return_value=None):
-            snapshot = load_queue_snapshot()
+        with mock.patch.dict("os.environ", {"WEBUI_TEST_OFFLINE": "0"}):
+            with mock.patch("webui.queue_loader.get_auth_header", return_value=None):
+                snapshot = load_queue_snapshot()
         self.assertIsNotNone(snapshot.fetch_error)
         self.assertEqual(len(snapshot.prs), 0)
 
@@ -285,4 +286,4 @@ class TestQueueFailClosedUx(unittest.TestCase):
 
 
 if __name__ == "__main__":
-    unittest.main()
+    unittest.main()