[FR] Make location of `.shell-ai` configurable

[nbbaier]

I love this tool (and use it every day)! But I do have a small QOL feature request: make it possible to change the location of the configuration directory. I find it very frustrating to have a bunch of dotfiles in my $HOME, and would love ot move it to ~/.config/shell-ai or something similar.

I think this would be a pretty minimal change if you make it configurable with an environment variable that defaults to ~/.shell-ai when it's unset. Happy to open a PR if that's a welcome change!

[ibigio]

Hey Nico! I'm actually working on a major update to the config setup, (in part to support gpt5), which includes moving it to .config :)

So awesome to hear you're using this every day!!

[nbbaier]

Very cool! Looking forward to seeing the update. Really great tool!