test: assert SA key file path is forwarded in GCP detector

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

Author: cloudsmith-iduffy

cloudsmith_cli/core/tests/test_gcp_detector.py

@@ -122,7 +122,8 @@ def test_returns_token_from_key_file(self):
             get.side_effect = requests.exceptions.ConnectionError()
             token = make_detector().get_token()
         assert token == "sa-jwt"
-        _, kwargs = from_file.call_args
+        args, kwargs = from_file.call_args
+        assert args[0] == "/tmp/key.json"
         assert kwargs["target_audience"] == "cloudsmith"
         fake_creds.refresh.assert_called_once()