Docs Cleanup and CLAUDE.md Routing

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 against context architecture: the checker passes and nothing was stale, duplicated or unrouted, so there is no PR. 5 routing-gap advisories left (informational, false positives).