Add `CLAUDE.md`

## Description

Add a `CLAUDE.md` file to this repository to provide repository-specific context and guidance when working with Claude Code.

The structure and expected content for `CLAUDE.md` are being defined in insightsengineering/nestdevs-tasks#121. The implementation should follow the agreed structure from that issue and adapt the content to this repository.

The `CLAUDE.md` should capture the relevant repository-specific information while following the common conventions agreed for the teal repositories.

## Acceptance criteria

* `CLAUDE.md` is added to the repository.
* The file follows the structure agreed in insightsengineering/nestdevs-tasks#121.
* Repository-specific guidance is included where relevant.

Start by reviewing the agreed CLAUDE.md structure in insightsengineering/nestdevs-tasks#121, then inspect this teal.slice repository for relevant repository-specific context. Add CLAUDE.md at the repository root using the agreed structure and include applicable guidance; done means all three acceptance criteria are met.

Written by the indexing model from the issue text.