Clean up and consolidate obsolete 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 audit found the tree already clean (checker green, all docs reachable, no dangling ADRs, no stale trackers). Removed dated/task-id narration from the package-distribution doc. PR #7298 queued; quick gate green. Memory: none applied.