Scrub and consolidate documentation under CLAUDE.md

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 audited (all ADRs, policies, portfolio, specs): already current-state. Merged PR #5354 removing two redundant ADR lines. Local full gate had 2 unrelated load failures; PR CI green. Optional ADR trims deferred.