Refactor VuMark tests to use verify_mock_vuforia fixture

Use the standard test pattern with the verify_mock_vuforia fixture so
tests run against all backends (real, mock, docker). Add test classes
to the CI matrix in test.yml.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Author: adamtheturtle

.github/workflows/test.yml

@@ -111,6 +111,10 @@ jobs:
           - tests/mock_vws/test_update_target.py::TestUpdate
           - tests/mock_vws/test_update_target.py::TestWidth
           - tests/mock_vws/test_update_target.py::TestInactiveProject
+          - tests/mock_vws/test_vumark_generation.py::TestSuccessfulGeneration
+          - tests/mock_vws/test_vumark_generation.py::TestInvalidAcceptHeader
+          - tests/mock_vws/test_vumark_generation.py::TestInvalidInstanceId
+          - tests/mock_vws/test_vumark_generation.py::TestResponseHeaders
           - tests/mock_vws/test_requests_mock_usage.py
           - tests/mock_vws/test_flask_app_usage.py
           - tests/mock_vws/test_docker.py