Rewrite crate-workspace.md from a migration checklist into binding layout law: why four packages, naming (core package / misaligned lib), dependency edges including Bevy→assets mesh share, gate mapping, and rejected alternatives. architecture.md points at that page for why and mirrors as-built paths only. Defense: Living-spec corpus rule — current package architecture lives on the owning Type: spec page with design reasons attached, not only in session history.