AI-first Git CLI automation — atomic AI commits, co-change relations, autonomous git health agent, pre-tool hook safety, and workspace initialization

Portable core of Sam's Claude Code setup: native pre-commit hook enforcement (sentinel gate retired 2026-08-14), on-demand /validate, generic review agents, cross-model Codex review skills, and a /bootstrap-cc-setup skill that writes the always-loaded rules layer plugins cannot ship. For repos NOT bootstrapped by the Loam Copier template - a Loam-rendered project already carries most of this in .c