0.0.20.9 - Surface infestation foliage/crop compatibility

Problem:
Corpse/remains/blood placement required air, so grass, flowers and crops could block death-spawned infestation.

Implementation:
- DeathSurfacePreparationMixin runs only when the existing converted/non-converted death procedures execute.
- SurfaceInfestationCompat checks the same local death footprint (max radius 3), removes non-solid plant/crop states with drops enabled, and leaves solid terrain alone.
- Plant recognition prefers the vanilla/Forge plant class hierarchy, with conservative registry-name fallbacks for custom modded flora.
- 15 ticks later, farmland is converted to minecraft:dirt only where a Phayriosis corpse/remains/blood/acid surface block actually exists.
- No world tick polling was added.

Validation targets:
- vanilla short/tall grass and flowers
- vanilla wheat/carrot/potato/beetroot fields: crop drops, farmland -> dirt under infestation
- several modded flowers/crops
- ordinary solid blocks must never be removed by the foliage preparation pass
