DDL

Promote /validate to canonical, formalize Codex Runtime Contract, add README-as-design

Restructure Codex skills for multi-agent support and fix command paths

Fix Scribe draft step numbering, realize dep checks, and PDF CJK font pipeline

Establish ISA and compilation model in Scribe document-writing skill

Fix Loop diagram: output file is a Human & LLM edit point, not one-way output