feat(core): reachable SW landmark chamber demo with a reachability audit (L45); research R12

Stamp vocabulary v2; the flagged SW demo opens through a side-facing portal and a bent ramp (max 14 deg,
two landings) into a 17 x 15 m chamber with a rock dais. New reachability audit: a capsule surface search
from walkable ground near the arrival mouth to the chamber floor (66 samples, 0 blocked/unsupported); the
buried L43 layout fails it. Demo off: owner hashes identical to L44. fast/medium/full PASS (Clang+GCC).
Research R12 (read-only): composite cavern-graph generator design and slices.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_016dhxM43dnWvUu2B5Ph1iG1

Standalone/Core/src/ShapeWorldInternal.h

@@ -3339,6 +3339,10 @@ private:
                 return result;
             }
         QueryStampSpatialNode(0,minimum,maximum,result);
+        // Stamp union/carve composition follows canonical stable-ID order. The BVH query
+        // order is spatial and can differ per tile, which would let a later carve erase a
+        // fill on meshed tiles even though unscoped density queries use the canonical order.
+        std::sort(result.begin(),result.end());
         return result;
     }
 
@@ -5673,9 +5677,14 @@ private:
         case VoxelForgeCore::ResolvedSdfStampKindV1::fillPillar:
             distance=StampPillarSdf(localX,localY,localZ,stamp.halfExtentsVoxels);break;
         case VoxelForgeCore::ResolvedSdfStampKindV1::fillDais:
-            distance=StampRoundedBoxSdf(localX,localY,localZ,stamp.halfExtentsVoxels,
-                std::min(0.35f,std::min({stamp.halfExtentsVoxels[0],
-                    stamp.halfExtentsVoxels[1],stamp.halfExtentsVoxels[2]})*0.15f));break;
+            if(ResolvedLayout&&ResolvedLayout->stampVocabularyVersion
+                >=VoxelForgeCore::ResolvedLayoutStampVocabularyVersionV2)
+                distance=StampEllipsoidSdf(localX,localY,localZ,stamp.halfExtentsVoxels);
+            else
+                distance=StampRoundedBoxSdf(localX,localY,localZ,stamp.halfExtentsVoxels,
+                    std::min(0.35f,std::min({stamp.halfExtentsVoxels[0],
+                        stamp.halfExtentsVoxels[1],stamp.halfExtentsVoxels[2]})*0.15f));
+            break;
         default:return std::numeric_limits<float>::infinity();
         }
         if(stamp.irregularityAmplitudeVoxels>0.0f)