MixinMinecraftServer

Server-lane heartbeat + the server-stop reap, as a mixin.

The heartbeat pumps at the tick's RETURN (postfix) so the eval sees the fully-settled post-tick server state. RETURN callbacks run in the order their injectors are applied, and a high priority applies ours after other mods' of the same injector order — best-effort, since from Mixin 0.8.7 a higher order outranks any priority.

1_000_000_000, not Integer.MAX_VALUE: upstream Mixin, which Forge ships, sorts by this.priority - other.priority, and MAX_VALUE overflows that against any negative priority, which can break the ordering of every mixin on the class. This value can't overflow against a priority down to -1_147_483_647. Priority plays no part against an @Overwrite of tickServer: all mixins merge their members before any injector scans for targets, so the injection survives an overwrite of any priority.