Try & integrate Kapa

I've got an Open Source free access to [Kapa](https://www.kapa.ai).

Let's try and, if we like, let's integrate it.

@phonzammi I'd say highest prio after +choices (or in parallel to working on +choices if you prefer, as you wish).

The issue links Kapa and proposes trying its free access before deciding whether to integrate it. No files, tests, or entry points are named, so first inspect the repository structure and existing documentation integrations, then evaluate Kapa against the project’s needs. Done means the trial has a clear outcome and any integration scope is agreed.

Written by the indexing model from the issue text.