Add computeRooms + alertEnemiesInPlayerRoom: a gunshot now alerts every
idle guard sharing the player's room regardless of range/LOS/cone. A
door cell is always treated as a room boundary for this purpose, even
when fully open — two rooms joined only by a doorway stay distinct
("gunfire carries through the room, not through doorways").
Fix _guardFacing side-walk/side-idle flip: was `rel > 0`, read
backwards in-game, now `rel < 0`.
Cover with three verifyWolfenstein cases: same-room alert fires,
behind-closed-door does not, through-open-door does not (door forced
slide=1 / wall zeroed to exercise the slide-independent path).
