This PR documents the release notes writing process in detail and adds a
guard check to `release_checklist.py` to ensure release notes are
created for `-rc1` releases before proceeding with downstream repository
updates.
- **doc/dev/release_checklist.md**: Expanded "Writing the release notes"
section with detailed steps for generating, reviewing, and formatting
release notes in Verso format
- **script/release_checklist.py**: Added
`check_release_notes_file_exists()` to verify the release notes file
exists in reference-manual repository
- **.claude/commands/release.md**: Added "Release Notes" section
explaining the process for creating release notes during `-rc1` releases
🤖 Prepared with Claude Code
Co-authored-by: Claude Opus 4.5 <noreply@anthropic.com>