Documentation audit and consolidation for accessibility

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

Docs audit found the tree already clean (checker, selftest pass; no stale working files, history narration or dead ADRs). No changes, no PR. Memory: none applied.