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.

Read GitHub's CODEOWNERS documentation and inspect the repository structure to choose one of the suggested locations: /.github/CODEOWNERS, /CODEOWNERS, or /docs/CODEOWNERS. Add the file and ensure branch protection rules reference it where applicable; the owner and path patterns still need to be determined.

Written by the indexing model from the issue text.