Clean and consolidate stale 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

Re-audited docs (ADRs, specs, lessons, research, router reachability, duplicates) with checker and scripts; already scrubbed by prior commits, nothing stale found, no PR. Report uploaded. Memory: none applied.