Clean up and consolidate documentation architecture

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 compliant; the audit found nothing stale to delete, so no PR. Telemetry trace was not captured. Memory: none applied.