- ui-store syncs screens to history (push on go/goGame, hash URLs like #/profile),
back() = history.back(), initHistory anchors a home base + restores deep links
- page.tsx listens to popstate; resolveScreen() guards transient screens
(game/room/chat/matchmaking fall back to home when their state is gone)
- ScreenHeader + ChatScreen back buttons use history back; chat cleans up on unmount
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>