Proposal: Locale-aware localization for slash-command skills

Hi, thanks for maintaining this project.

I have been experimenting in my local fork with locale-aware localization for custom slash commands such as /office-hours, and I wanted to check whether this direction would fit the project before preparing a PR.

The scope is intentionally limited:
- only slash-command content is localized
- English remains the default
- language is selected at setup time from the user environment
- the mechanism is designed so additional languages can be added later

I have mainly tested this with Japanese so far, but the goal is broader multilingual support rather than a one-off customization.

Would this be a direction you would consider upstreaming? If so, I can prepare a small proof-of-concept PR for a single skill first.

Thanks.