docs: add credits section to contributing guide

[solomonneas]

Adds a short credits section to CONTRIBUTING.md noting the maintainer and that development runs through the multi-model seat roster, with co-author trailers on commits where a coding agent did substantial work.

Docs-only. Vale clean.

[coderabbitai]

Important

Review skipped

Auto reviews are limited based on label configuration.

🏷️ Required labels (at least one) (1)

• coderabbit-review

Please check the settings in the CodeRabbit UI or the .coderabbit.yaml file in this repository. To trigger a single review, invoke the @coderabbitai review command.

⚙️ Run configuration

Configuration used: Repository: escoffier-labs/coderabbit/.coderabbit.yaml

Review profile: CHILL

Plan: Pro Plus

Run ID: 8ba32237-42a9-4552-b525-6427a9541480

You can disable this status message by setting the reviews.review_status to false in the CodeRabbit configuration file.

Use the checkbox below for a quick retry:

• 🔍 Trigger review

✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch chore/credits

---

_{Comment @coderabbitai help to get the list of available commands.}