wip(assembler): round L29 -- strate transitions honoured at the bedrock/ceiling interface

EVoxelStrateTransition from the upper strate shapes the bedrock(N)/ceiling(N+1) interface in the
shared composition layer: Hard flat; Gradient = smooth 2D hash surface (16 m owner width, about 4 m
measured undulation); Interleaved = 3D domain-warped fingered overlap within the width. Each band
keeps >= 2 Core voxels solid; faces return to the seam near passage mouths. Interface audit over
512 m: 0 hole columns for all modes; wider-than-declared and too-thin controls rejected. All passage,
route, proof and validator audits pass; deterministic Clang = GCC. Evaluator 15. Cost +4% SW,
+1.3% FI vs L28. Open: ring-like artifact on the FI floor capture; transition look unverified.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01CSFYgsdW8ejZSyiMf4qRSX

Source/VoxelForge/Private/VoxelForgeCoreAdapter.cpp

@@ -1106,13 +1106,21 @@ bool AttachValidatedWorldAssembly(const UVoxelSettings* Settings,
         Item.transitionWidthMicrometres = static_cast<std::int64_t>(Item.transitionBlendChunks)
             * Item.managerChunkWidthMicrometres;
         Item.transitionWarpAmplitudeMicrometres = Item.transitionMode == "Interleaved"
-            ? 2 * Item.managerChunkWidthMicrometres : 0;
-        Item.transitionInterpenetrationMicrometres = 0;
-        Item.transitionHonouredInCore = Slot.Definition->TransitionType == EVoxelStrateTransition::Hard;
-        Item.transitionFallsBackToHard = Slot.Definition->TransitionType != EVoxelStrateTransition::Hard;
+            ? std::min(Item.transitionWidthMicrometres / 2, Item.managerChunkWidthMicrometres) : 0;
+        Item.transitionInterpenetrationMicrometres = Item.transitionMode == "Interleaved"
+            ? Item.transitionWidthMicrometres
+            : Item.transitionMode == "Gradient" ? Item.transitionWidthMicrometres / 4 : 0;
+        Item.transitionFallsBackToHard = Item.transitionMode != "Hard"
+            && Item.transitionWidthMicrometres <= 0;
+        Item.transitionHonouredInCore = Item.transitionMode == "Hard"
+            || !Item.transitionFallsBackToHard;
         Item.transitionDispatchPath = Item.transitionFallsBackToHard
-            ? "declared Gradient/Interleaved recorded; Core uses an explicit Hard transition fallback with zero interpenetration"
-            : "declared Hard transition is applied at this interface";
+            ? "declared zero-width transition uses an explicit Hard fallback"
+            : Item.transitionMode == "Hard"
+                ? "declared Hard transition preserves the flat shared bedrock/ceiling interface"
+                : Item.transitionMode == "Interleaved"
+                    ? "shared composition overlaps both facing bands with deterministic domain-warped fingers inside the declared width"
+                    : "shared composition moves both band faces together with the smooth declared-width transition field";
         Item.managerLookup = "UVoxelStrateManager::GetGeneratorTypeForChunk; transition is controlled by upper strate";
         if (Type == ECaveGeneratorType::SurfaceWorld)
         {

Source/VoxelForge/Public/VoxelStrateTypes.h

@@ -201,15 +201,19 @@ enum class ECaveGeneratorType : uint8
 };
 
 /**
- * EVoxelStrateTransition — How two adjacent strates blend at their shared boundary.
+ * EVoxelStrateTransition — How two adjacent strates meet at their shared boundary.
  *
  * Each strate boundary can use a different transition style. The transition type
  * is defined on the UPPER strate's definition and controls the boundary between
  * itself and the strate below it.
  *
- * Gradient:    Smooth linear interpolation of generation params across TransitionBlendChunks.
- *              This is the classic approach — no seam visible, but also no dramatic
- *              geological feature at the boundary. Best for similar-looking strates.
+ * In the Core composition path, TransitionBlendChunks defines the full permitted
+ * crossing depth between the upper bedrock and lower ceiling bands. Each band keeps
+ * its authored thickness and the solid bands always overlap or touch. The legacy manager
+ * may also blend generation parameters for Gradient; Core does not blend unrelated fields.
+ *
+ * Gradient:    A low-amplitude smooth height field moves the shared interface and both
+ *              content-facing band surfaces. Best for gentle geological variation.
  *
  * Hard:        No blending at all. The strate's params apply right up to the boundary,
  *              then instantly switch to the neighbor's params. The abrupt change in
@@ -217,26 +221,21 @@ enum class ECaveGeneratorType : uint8
  *              discontinuity at the boundary. Best for strates that should feel like
  *              distinct geological layers with a visible dividing line.
  *
- * Interleaved: The boundary position is warped by a 3D noise field, so "fingers"
- *              of one strate reach into the other. Some XY columns transition early,
- *              others late, creating an irregular, interlocking boundary. The warp
- *              amplitude is ~2 chunks, and Z frequency is lower than XY to produce
- *              horizontal finger-like intrusions. Best for strates that should feel
- *              like they grew into each other over geological time.
+ * Interleaved: A deterministic 3D domain-warped hash field sets the overlap depth per XY
+ *              column from zero to the declared width, creating irregular fingers.
+ *              Best for strates that should feel grown together.
  */
 UENUM(BlueprintType)
 enum class EVoxelStrateTransition : uint8
 {
-    // Smooth linear interpolation of all generation params across the blend zone.
-    // No visible boundary — params change gradually over TransitionBlendChunks distance.
+    // Smoothly undulates the shared bedrock/ceiling interface in the Core composition path.
     Gradient    UMETA(DisplayName = "Gradient (smooth blend)"),
 
     // No blending — params switch instantly at the boundary.
     // Creates natural cliffs, ledges, or material discontinuities.
     Hard        UMETA(DisplayName = "Hard (sharp boundary with cliff)"),
 
-    // 3D noise warps the boundary position per XY column.
-    // Creates finger-like intrusions of one strate into the other.
+    // A 3D domain-warped hash field creates finger-like intrusions within the declared width.
     Interleaved UMETA(DisplayName = "Interleaved (domain-warped fingers)")
 };