fix(unreal): U1 -- Unreal compiles again on L61; CoreGeometry asset section; versioned layout-unit upgrade

Windows MSVC catch-up after abyss L15-L61 (no Unreal there): 64-bit clipmap
shift (C4334), qualified VoxelForgeCore::WorldAssemblySubvoxelsPerVoxel, UHT
metadata and duplicate-signature fixes. Optional CoreGeometry section on
UVoxelStrateDefinition (native caves, lattice, profiled heightfields, named
stamps, rooms/tunnels; off/empty by default), resolved after passage planning.
VoxelForgeAssetVersion 2 converts strate height/transition/gap to metres on
load (exact, 0 m change on the owner's 5 assets; packages never saved).
Gates pass (SurfaceWorld, FloatingIslands, Core-off, M2, W1/W8/W16).
KNOWN REGRESSION vs L14 (2026-10-20, same command, same PC): full set 3.9 ->
5.37 s, worker-seconds 15.8 -> 30, LOD0 1.11 -> 1.69 s, ring 0.50 -> 0.80 s;
not yet attributed (Core L15-L61 vs Unreal side).
Report: Standalone/Research/WorldAssemblerM3/Unreal1.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

Source/VoxelForge/Private/VoxelSettings.cpp

@@ -1,5 +1,7 @@
 #include "VoxelSettings.h"
 
+#include "VoxelForgeAssetVersion.h"
+#include "VoxelStrateDefinition.h"
 #include "VoxelSeasonAsset.h"
 
 #if WITH_EDITOR
@@ -9,6 +11,74 @@
 #include <VoxelForgeCore/VoxelForgeCore.h>
 #include <string>
 
+void UVoxelSettings::Serialize(FArchive& Ar)
+{
+    Ar.UsingCustomVersion(VoxelForgeAssetVersion::GUID);
+    Super::Serialize(Ar);
+    if (Ar.IsLoading() && Ar.CustomVer(VoxelForgeAssetVersion::GUID)
+        < VoxelForgeAssetVersion::MetreAuthoringV1)
+    {
+        const double LayoutChunkMeters = FMath::IsFinite(StrateLayoutChunkSizeMeters)
+            ? FMath::Max(0.001, static_cast<double>(StrateLayoutChunkSizeMeters)) : 8.0;
+        InterStrateGapMeters = static_cast<double>(FMath::Max(0, InterStrateGapChunks))
+            * LayoutChunkMeters;
+        UE_LOG(LogTemp, Display,
+            TEXT("[VoxelForgeAssetUpgrade] type=Settings asset=%s gap_chunks=%d gap_m=%.6f layout_chunk_m=%.6f"),
+            *GetPathName(), InterStrateGapChunks, InterStrateGapMeters, LayoutChunkMeters);
+    }
+}
+
+void UVoxelSettings::PostLoad()
+{
+    Super::PostLoad();
+    if (GetLinkerCustomVersion(VoxelForgeAssetVersion::GUID)
+        >= VoxelForgeAssetVersion::MetreAuthoringV1)
+    {
+        return;
+    }
+
+    // Resolve the legacy count against this settings asset's saved physical layout width.
+    // Convertit les anciens comptes avec la largeur physique sauvegardee dans ces reglages.
+    const double LayoutChunkMeters = FMath::IsFinite(StrateLayoutChunkSizeMeters)
+        ? FMath::Max(0.001, static_cast<double>(StrateLayoutChunkSizeMeters)) : 8.0;
+    InterStrateGapMeters = static_cast<double>(FMath::Max(0, InterStrateGapChunks))
+        * LayoutChunkMeters;
+
+    TSet<UVoxelStrateDefinition*> Migrated;
+    const auto MigrateStrate = [this, LayoutChunkMeters, &Migrated](
+        const TSoftObjectPtr<UVoxelStrateDefinition>& SoftDefinition)
+    {
+        UVoxelStrateDefinition* Definition = SoftDefinition.LoadSynchronous();
+        if (Definition == nullptr || Migrated.Contains(Definition)
+            || Definition->GetLinkerCustomVersion(VoxelForgeAssetVersion::GUID)
+                >= VoxelForgeAssetVersion::MetreAuthoringV1)
+        {
+            return;
+        }
+        Migrated.Add(Definition);
+        const int32 OldHeightChunks = Definition->StrateHeightInChunks;
+        const int32 OldTransitionChunks = Definition->TransitionBlendChunks;
+        Definition->StrateHeightMeters = static_cast<double>(FMath::Max(1, OldHeightChunks))
+            * LayoutChunkMeters;
+        Definition->TransitionWidthMeters = static_cast<double>(FMath::Max(0, OldTransitionChunks))
+            * LayoutChunkMeters;
+        Definition->MarkPackageDirty();
+        UE_LOG(LogTemp, Display,
+            TEXT("[VoxelForgeAssetUpgrade] type=Strate asset=%s height_chunks=%d height_m=%.6f transition_chunks=%d transition_m=%.6f effective_layout_chunk_m=%.6f"),
+            *Definition->GetPathName(), OldHeightChunks, Definition->StrateHeightMeters,
+            OldTransitionChunks, Definition->TransitionWidthMeters, LayoutChunkMeters);
+    };
+    for (const TSoftObjectPtr<UVoxelStrateDefinition>& Definition : StratePool)
+    {
+        MigrateStrate(Definition);
+    }
+    for (const TPair<int32, TSoftObjectPtr<UVoxelStrateDefinition>>& Definition : FixedStrates)
+    {
+        MigrateStrate(Definition.Value);
+    }
+    MarkPackageDirty();
+}
+
 int32 UVoxelSettings::GetEffectiveWorldSeed() const
 {
     if (!Season.IsNull())