Clean up and consolidate scattered documentation

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 the docs per context-architecture skill: no stale/orphan/duplicate docs found; no changes needed, no PR. Memory: none applied.