0.0.20.13 - Exact-target death foliage replacement

Problem:
The radius-3 foliage preparation in 0.0.20.12 correctly allowed infestation placement, but it removed every eligible plant in the possible death footprint even when no death-generated block actually landed there.

Fix:
- SurfaceInfestationCompat.prepare is now intentionally a no-op; there is no pre-clearing radius scan.
- Death-procedure target AIR gates now treat only replaceable foliage at the exact attempted target as occupiable.
- Support/below-space isAir checks are deliberately left unchanged.
- SurfaceInfestationCompat.place removes foliage only at the exact successful/attempted placement position.
- Replaced foliage uses destroyBlock(..., false), so no item entities are spawned.
- Existing exact farmland-under-successful-infestation -> dirt behavior is unchanged.
- No delayed jobs, world scans, or tick listeners were added.
- Xaero compatibility from 0.0.20.11/12 is untouched.
