Complete documentation set for the facade migration (B1-R6) and beyond:
facade-migration-roadmap, handoffs v3-v6, R5 guides, R6 cleanup plan,
R7 pure-ABI plan, long-term plans (riir/ai-agent/gtest/ui-redesign),
updated Chinese README draft, UI design mockups, and the Google Test +
struct-typedef rules in CONTRIBUTING.
