docs: feature public YouTube introduction and 4K thumbnail
docs: publish SYSTEMX introduction film and 4K poster
docs: publish white paper edition 2.0 manual
Document alpha.3 hardening and verified release in wiki
Document Agent Y CLI channels and 1.9.0 alpha.2 release
Document 1.8.7 alpha release and security boundaries
Use organized media paths and latest-only galleries
Document illustrated research edition and publication format
Document expanded white paper, technical reference and audio companion
Add white paper and update public documentation for 1.8.3 alpha