Add a CODEOWNERS file

This repository does not currently include a `CODEOWNERS` file.

A `CODEOWNERS` file helps:
- ensure reviewers are automatically requested,
- clarify ownership and on-call responsibilities,
- enforce code review policies via branch protection rules.

**Suggested locations (choose one):**
- `/.github/CODEOWNERS` *(preferred if sharing across many repos via a central file)*
- `/CODEOWNERS`
- `/docs/CODEOWNERS`

**Docs:** https://docs.github.com/repositories/managing-your-repositorys-settings-and-features/customizing-your-repository/about-code-owners

Please add a `CODEOWNERS` file and ensure branch protection rules reference it where applicable.

Start with GitHub's CODEOWNERS documentation and choose one of the suggested locations, preferably /.github/CODEOWNERS. Determine the repository's ownership entries and check whether branch protection rules need to reference the file. Done means the CODEOWNERS file is present in the chosen location and applicable review settings use it.

Written by the indexing model from the issue text.