📝 Documentation: Split docs site into 'CLI' and 'Engine'

[JoshuaKGoldberg]

Bug Report Checklist

• I have pulled the latest main branch of the repository.
• I have searched for related issues and found none that matched my issue.

Overview

Documenting a tool like create is tricky because there are really two tools in one:

• The CLI: what 99.99999% of users care about
• The underlying engine: where much of the complexity and concepts reside

Right now the docs sidebar tree only kind of reflects that. CLI information is all root-level; engine information is inside a collapso:

But I think these should be separated even more. I think there should be two docs sections: one for CLI and one for Engine.

Additional Info

For reference, typescript-eslint.io has a similar split right now between Docs and Rules.

I'm separately ramping up on the Yeoman/Yo project and am now wondering if this same split is why they have an explicitly different name for the core project ("yeoman") and the CLI ("yo")...

💝

[JoshuaKGoldberg]

This isn't yet natively supported in Starlight core: withastro/starlight#959. withastro/starlight#687 (comment) suggests using component overrides.

Alternately, comments in that discussion point to some userland approaches. I like the look of https://github.com/HiDeoo/starlight-sidebar-topics.