Adds `.coderabbit.yaml` with `reviews.auto_review.ignore_usernames:
["dependabot[bot]"]` so CodeRabbit stops reviewing and commenting on
Dependabot PRs. Config-only change; same file is landing across the
craft repos.
🤖 Generated with [Claude Code](https://claude.com/claude-code)
Co-authored-by: Claude Opus 5.5 <noreply@anthropic.com>
