Re-enable the system plugin license check with a LICENSE_TYPE constant.
Set to 'free' — check exits immediately with zero overhead. Change to
'pro' to enable download key validation. Update plugin descriptions
and CLAUDE.md to document the licensing model.
Authored-by: Moko Consulting
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>