3-floor Elevator (Moore FSM)

Three states: IDLE, GOING_UP, GOING_DOWN. i_target(1:0) is the requested floor (00=F1, 01=F2, 10=F3). i_floor(1:0) is the current position. If target > floor, go up; if target < floor, go down; else stay idle. o_run='1' when moving, o_dir='0' for up, o_dir='1' for down.