Reworked terrain transitions

- New terrain heights meet saved boundaries while retaining local relief
- Surface water levels approach saved fluid heights across the band
- Cave and physical biome matching use a four-block seam patch
- Terrain generates once without speculative neighbor containment
- Bounded caches serve transition membership and boundary lookups
- Saved biome writes honor the selected durability policy
- Release labels and presentation code leave generation identity unchanged
- Unfinished objects retain blocks and metadata across pack changes
- Whole structure assemblies preserve pending excavation and foundations
- New placements keep pending historical pieces clear
- Transition probes cover cutovers and retained object fragments

adapters/modded-common/src/main/java/art/arcane/iris/modded/IrisModdedChunkGenerator.java

@@ -66,7 +66,6 @@ import art.arcane.iris.world.history.TerrainNativeBlockKeys;
 
 import art.arcane.volmlib.nativelib.terrain.NativeChunkWritePolicy;
 
-import art.arcane.iris.world.history.TerrainBoundarySignature;
 import art.arcane.iris.world.history.NativeBiomeSpawnSelection;
 import art.arcane.iris.pack.loading.IrisData;
 import art.arcane.iris.pack.PackValidationRegistry;
@@ -1086,7 +1085,7 @@ public final class IrisModdedChunkGenerator implements NativeGeneratorOwner, Nat
 
     @Override
     public NativeBlockColumn resolvedColumn(Engine current, int x, int z) {
-        return current.getComplex().resolvedTerrainColumn(x, z).map(TerrainBoundarySignature::geometry).orElse(null);
+        return null;
     }
 
     @Override

adapters/modded-common/src/main/java/art/arcane/iris/modded/ModdedNativeStructurePolicy.java

@@ -102,7 +102,8 @@ final class ModdedNativeStructurePolicy implements NativeModdedStructureStage.Po
 
     @Override
     public NativeBlockPositionPredicate protectedPositions(Engine context) {
-        return GenerationWritePolicy.protectedPositions(context.getDimension().getStaticObjectLayer(context.getData()),
+        return GenerationWritePolicy.protectedPositions(context.getDimension().getStaticObjectLayer(context.getData())
+                        .forTransition(context),
                 context.getDimensionStackContext(), context.getMinHeight());
     }