wip(assembler): M1 repair round -- raised block and cliff fixed; native 7x faster than legacy

Luna, M1 repair round: the rectangular raised block and the broken cliff shared one cause,
a type-2 solid AABB in the generated plan; it is now a tapered, terrain-following shelf, and
a negative-control audit catches the old box behaviour; seam classification check passes.
Bound audit 298 boxes / 8,046 samples, 0 misses. Evaluator and 120-tile density/mesh/payload/
topology hashes identical at W1/W8/W16. Cave regression: walkability 5,642/5,642, 64/64 tiles.
Legacy mismatch unchanged (0 biome mismatches, 18.14% signs).
Speed (matched workloads): 120-tile full detail 0.089 s native vs 0.625 s legacy; 529-tile
clipmap 3.858 s vs 11.687 s -- 2.29 s above the ~1.57 s aim; LOD8 dominates (165 unknown
tiles, 13.27 M field calls, 10.88 M column-cache misses).
My capture review: coast matches legacy closely; surface clean but a dark flat slab on the far
horizon; cliff shelf renders as a stack of thin plates with back faces showing (sub-voxel
shelf thickness suspected).

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01MmSoF64BbRFmk9C3p1VsBJ

Standalone/Source/StreamingWorld.h

@@ -57,6 +57,7 @@ struct FStandaloneCpuTile
     uint64 TopologyHash=14695981039346656037ull;
     bool bHasTopologyHash=false;
     uint64 MeshPayloadAllocatedBytes=0;
+    VoxelForgeCore::TileGenerationStats CoreDiagnostics{};
     std::array<uint64,VoxelDensityProfile::BucketCount> ProfileCycles{};
 
 };
@@ -417,7 +418,7 @@ public:
                                            bool bInSkipUV=false,
                                            bool bInSkipColors=false,
                                            VoxelForgeCore::World* InCoreWorld=nullptr)
-        :World(&InWorld),WorkerCount(FMath::Clamp(InWorkerCount,1,8)),bHashDensity(bInHashDensity),
+        :World(&InWorld),WorkerCount(FMath::Clamp(InWorkerCount,1,16)),bHashDensity(bInHashDensity),
          MeshCache(InMeshCache),MaxLevelFilter(InMaxLevelFilter),
          CoreWorld(InCoreWorld),bSkipUvAndColors(bInSkipUvAndColors),bSkipMaterialGroups(bInSkipMaterialGroups),
          bSkipUV(bInSkipUV),bSkipColors(bInSkipColors)
@@ -736,6 +737,7 @@ private:
                 Out.CompletedAt=FClock::now();return Out;
             }
             Out.DensitySamples=Result->densitySampleCount;
+            Out.CoreDiagnostics=Result->diagnostics;
             Out.SurfaceVertexCount=Result->groups.surfaceVertexCount;
             Out.SkirtTriangleCount=Result->groups.skirtTriangleCount;
             Out.MeshPayloadAllocatedBytes=Result->meshPayloadAllocatedBytes;