fix file descriptor leak in cmd.run()

we were leaking pipes.

pkgs/clan-cli/pyproject.toml

@@ -35,6 +35,7 @@ log_format = "%(levelname)s: %(message)s\n       %(pathname)s:%(lineno)d::%(func
 addopts = "--cov . --cov-report term --cov-report html:.reports/html --no-cov-on-fail --durations 5 --color=yes --new-first -n auto" # Add --pdb for debugging
 norecursedirs = "tests/helpers"
 markers = ["impure", "with_core"]
+filterwarnings = "default::ResourceWarning"
 
 [tool.mypy]
 python_version = "3.12"