Use via.OnKeyDownMap for snake keybindings, replacing the manual
dataExpr/rawDataAttr workaround. Window-scoped key handling removes
the need for tabindex/focus hacks, and WithPreventDefault on arrow
keys prevents page scrolling during gameplay.
Introduce a 60 FPS tick loop with a separate snake movement speed
(7 cells/s) so direction input is polled every frame but game state
only advances at the configured rate.
038c4b3f22