[richardcase]

What this PR does / why we need it:

This PR adds two files to the root of the repository.

• AGENTS.md gives the rules for all contributors and for coding agents. The file has a short description of the project, the make commands, and the rules for commits and pull requests.
• CLAUDE.md contains only @AGENTS.md. Claude Code reads this line and loads the rules from AGENTS.md. There is one copy of the rules.

The rules for commits are:

1. All commit messages must obey the Conventional Commits format.
2. All commits must have a valid signature.
3. Commit messages and pull request descriptions must not contain agent attribution lines.

Which issue(s) this PR fixes:
None

Special notes for your reviewer:

The commit in this PR obeys the three rules. It has a conventional subject, a GPG signature, and no agent attribution.

Checklist:

• squashed commits into logical changes
• includes documentation