Two modes: 'optional' (gentle CLAUDE.md suggestion) and 'required'
(CLAUDE.md enforcement + .claude/hooks/check-gstack.sh PreToolUse hook
that blocks work without gstack installed). Atomic JSON writes,
idempotent, prints git add instructions.
Part of team-install-mode feature (credit: Jared Friedman).
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>