Clean and consolidate outdated documentation system

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

Audited docs per context-architecture skill: already clean, nothing stale or duplicated to delete; no PR. Memory: none applied.