Pytest issue on Windows Pyinstaller-built executable tests

[aplowman]

E.g.: https://github.com/hpcflow/hpcflow-new/actions/runs/16303998548/job/46045520085

See: pytest-dev/pytest#11904, for what appears to be the same issue, although a linked PR indicates the issue should be fixed.

[aplowman]

This seems to be only for the single-file executables. We run the tests on the directory executables as part of the release workflow, and that seems to work fine with the same versions of Python, and pytest: https://github.com/hpcflow/hpcflow-new/actions/runs/16440555297/job/46460207184