It should be trivial to combine ephemeral options with file name options, which seems like it would be the best of both world.

With some agreement on mapping (maybe just `%HH` for anything outside `A-Z a-z 0-9 . _ -`), this could be completely standardized and made part of standard library argument parsers.

I could see a bunch of my utility scripts replaced with a python script and a `uv` shebang if this was in argparse.