Consolidate and clean up documentation architecture

Use context architecture skill to scrub all old documentation, including instructions, specs, trackers, ADRs - delete everything superseeded and stale, remove references to historical decisions, delete duplicates, single home everything and make sure all documentation is accessible from CLAUDE.md router in a few steps

Context-architecture audit of docs/, ADR register, lessons, specs, router: already clean, nothing stale to delete. Memory: none applied