TPG.Rush.Begin

Start a Rush round, or clear Rush state if this round is something else. Called unconditionally from tpg.rounds.Setup every round -- the same pattern as TPG.CTF.SpawnFlags -- so the round loop does not have to know which modes need setting up. Runs AFTER TPG.Objectives.SpawnAll has already spawned the round's full objective list, and deliberately replaces it: Setup spawns whatever the map lists for the game type, and Rush wants one point rather than all of them.