Flattening tests in test_cli.py

[pydanny]

While this looks like a HUGE change, in reality it is minimal. What it does:

1. Replaces use of the tempfile.TemporaryDirectory() context processor with the tmp_path pytest fixture, which provides a Path object instead of a string
2. Using this fixture flattens the code, making it easier to read and maintain

Note

This will be pulled out of draft once the other tests are converted to use tmp_path

[jph00]

@algal looks like there's some minor changes still needed based on the description before this can be merged.

[algal]

@jph00 Yeah. I think this is still marked draft becaase it's not complete. It's not ready for review or merge.