Try setting shell on Windows test runners

Author: tleonhardt

.github/workflows/tests.yml

@@ -36,6 +36,8 @@ jobs:
         run: uv sync --all-extras --dev
 
       - name: Run tests
+        if: runner.os == 'Windows'
+        shell: cmd
         run: uv run python -Xutf8 -m pytest --cov --cov-config=pyproject.toml --cov-report=xml tests
 
       - name: Upload test results to Codecov