Heartbeat

Server-lane heartbeat, standing in for the mod path's tickServer RETURN injection. Its own listener, so onEnable's registerEvents(this, this) doesn't register it early.

ServerTickEndEvent fires after runAllTasks() and before the loop's waitUntilNextTick(), so an eval sees the settled tick within the same tick. A runTaskTimer(0, 1) pump would observe the same state but only after that sleep — 50ms - MSPT later, i.e. worst on an idle server.

MONITOR, registered once the server has loaded, runs this after every tick listener registered by then; one registered later still lands behind it. It cannot order us against mods, which inject at the method's RETURN and therefore still run after this event.