Gravestone × Sable Compatibility Patch

A minimal patch mod for Minecraft 1.21.1 / NeoForge that fixes gravestone
placement when a player dies on a Sable sub-level (e.g. a Create Aeronautics
airship). Without this mod, dying mid-flight makes gravestone place its block
(and a dirt support block) in the parent world at the player's visible position.
The blocks then clip into the airship's collision shape and stall its physics.

With this mod installed, the grave is placed inside the airship's plot area, so
it lands on the deck and travels with the airship like any other block on it.