The player-centered camera snapped the dungeon to the top-left corner after a while: the
renderer nulled focusPoint on a transient player-less frame, so the transform lost its
translate. Fix: focusPoint is now sticky (keep the last if the player is momentarily
absent), and the SP bridge re-applies the camera every frame via its own RAF loop, so a
canvas resize or a stale frame can no longer break centering.