check-changelogs

Verify that each plugin has a CHANGELOG.md with an entry for the current version from plugin.json. Use when (1) before creating a pull request or release to ensure version history is documented, (2) after bumping version numbers with bump-version, (3) when asked to verify project health or release readiness, (4) during release preparation to confirm all changes are documented, (5) as part of comprehensive validation alongside check-versions and check-skill-counts, (6) when onboarding a new plugin to ensure proper version documentation.