Created MAC governance hub and source layout

Property	Value
description	Rebuilt `MAC` as the canonical governance and source repo for the MAC ecosystem.
version	0.4.0
type	Create
related	MAC, Repo Boundaries

• Rebuilt mac as the canonical governance and source repo for the mac-* ecosystem.
• Added first-class governance/, registry/, libraries/, and .codex/ layers for shared doctrine and reusable ecosystem skills.
• Replaced the older scattered top-level guideline, policy, template, prompt, and example model with a governance-first source layout.