The Ruff check recursive scan doesn't read non *.py files

[praiskup]

E.g. on our own directory, there's:

$ ruff check .
warning: No Python files found under the given path(s)
All checks passed!

This was better before 38412fb because
there we explicitly selected the (changed) files (vcs-diff-lint reads shebang):

$ ruff check vcs-diff-lint-csdiff-* vcs-diff-lint
All checks passed!

See also astral-sh/ruff#13122

[praiskup]

Mitigated by 62f4e65