Skills go stale as APIs change and data sources move. This adds a three-layer
staleness detection system: review date tracking with git fallback, HTTP health
checks for declared dependencies, and top-level key comparison for schema drift.
All new frontmatter fields are optional — existing skills work unchanged.
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
Adds skill_registry.py CLI tool with 7 subcommands (init, publish, list,
search, install, info, remove) for managing a git-friendly shared skill
catalog. No new dependencies — stdlib only. Integrates with existing
validate.py and security_scan.py for publish-time checks.
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
