Improve documentation for `generate-shell-completions`

[zanieb]

This command needs a longer doc comment for reference documentation.

[FishAlchemist]

This might be unrelated to the issue. Have you considered providing usage instructions for shell-completions, similar to pixi? https://pixi.sh/latest/#autocompletion

Or simplify it into a Starship way, output the auto-completed string, and then execute it.

Invoke-Expression (&starship init powershell)

> starship init powershell
Invoke-Expression (& 'C:\Program Files\starship\bin\starship.exe' init powershell --print-full-init | Out-String)

Invoke-Expression: https://learn.microsoft.com/en-us/powershell/module/microsoft.powershell.utility/invoke-expression Starship: https://starship.rs/

[zanieb]

No, but we should document it similar to pixi.

[zanieb]

Related https://github.com/astral-sh/uv/issues/2191