Clean up and consolidate outdated documentation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

Docs already conform: checker and selftest green, every doc within 2 hops of CLAUDE.md, no stale ADRs or trackers, no history narration. Nothing to delete; no PR. Memory: none applied.