Introduces the release-changelog skill (skills/release-changelog/SKILL.md)
that teaches agents to generate user-facing changelogs from git history,
changesets, and merged PRs. Includes breaking change detection, categorization
heuristics, and structured markdown output template.
Also creates the releases/ directory convention for storing versioned
release notes.
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>