AGENTS.md notes on the themes, plain CSS for container queries and
driving the app in Chrome; TODO.md gets the mobile app and rematch as
open work; the spec is marked implemented.
Backend README (GAME_CLOCK_MS), AGENTS.md notes, TODO items for the open points and the mobile release order; game-history R3.3 and R3.4 marked as replaced. Checked end to end in Chrome: moves, a backend restart, a timeout and the replay.