Adds ASSETS.md, NOTICE.md, per-directory READMEs, third-party license
texts, a CI check that notices don't rot, and README forking-guideline
updates. Carves commissioned artwork, the licensed icon system, and
Bluesky marks out of the blanket MIT license. See LEGMS-208.
Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
Samuel Newman