PacketTerrainImpactRenderer

Packet-only renderer for the shared cracked-terrain impact. The real world is never mutated: viewers receive temporary barrier block changes while packet BlockDisplays carry the copied block appearance through a small, deterministic scale-and-tilt animation. Barriers render invisible but keep the full-cube collision of the eligible surface blocks, so players standing in the impact do not fall into a client-side hole and get pulled back by the server every tick.