Add durable NUnit parity harness

.gitea/workflows/ci.yml

@@ -17,6 +17,8 @@ jobs:
           python3 tools/generate_rust_mapping.py --check
           python3 tools/generate_api_shims.py --check
           python3 tools/check_api_coverage.py
+          python3 tools/check_test_parity.py
+          python3 -m unittest discover -s tools -p 'test_*.py'
       - name: Formatting
         run: cargo fmt --all -- --check
       - name: Workspace check