Please implement `--version` or equivalent flag

I'm trying to figure out which version I have installed, but I can't. It would be very useful to have a `--version` argument print the current version and exit.

Thanks!

No file, test, or entry point is named in the issue. Start by locating the Python CLI entry point and its argument handling, then run the existing help or test commands to understand startup behavior. Done means a version flag prints the installed version and exits without starting the shell.

Written by the indexing model from the issue text.