fix: sanitizer sweep across all generators; bound signed shifts/division/overflow at coordinate limits (L61); R31

New verify.py sanitize tier (Clang address,undefined,float-cast-overflow; GCC address,undefined;
-fno-sanitize-recover) runs 19 cases per compiler at LOD0-8 across every generator, passages and the
crossing: 0 runtime reports; a planted signed-overflow control is caught by both. A static scan fixed
INT_MIN negation in floor division, unbounded signed LOD shifts and coordinate-times-extent overflow in
VoxelClipmapDesiredTiles.h and VoxelTypes.h (plugin and standalone), and VoxelWorld.cpp, VoxelContentManager.cpp
and VoxelDensityVolume.cpp (plugin only, uncompiled here). Supported-input output unchanged (version 211).
fast/medium/full PASS. Research R31 (self-checked): far-LOD 4-8 cut plan.

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

Source/VoxelForge/Private/VoxelDensityVolume.cpp

@@ -155,9 +155,11 @@ int32 UVoxelDensityVolume::NumLevels() const
 
 FORCEINLINE int32 UVoxelDensityVolume::FloorDiv(int32 A, int32 B)
 {
-    // True floor division (B > 0). FMath::DivideAndRoundDown truncates toward zero for negatives —
-    // a footgun the content manager hit too (see FloorDivPos there). Cells span the origin, so floor.
-    return (A >= 0) ? (A / B) : -(((-A) + B - 1) / B);
+    // True floor division (B > 0). Remainder adjustment handles INT_MIN without negating it.
+    if (B <= 0) { return 0; }
+    const int32 Quotient = A / B;
+    const int32 Remainder = A % B;
+    return Remainder < 0 ? Quotient - 1 : Quotient;
 }
 
 FORCEINLINE uint8 UVoxelDensityVolume::Quantize(float MCDensity)
@@ -180,7 +182,8 @@ void UVoxelDensityVolume::EnsureAllocated()
     for (int32 L = 0; L < N; ++L)
     {
         FClipLevel& Lv = Levels[L];
-        Lv.Step = 1 << L;
+        Lv.Step = static_cast<int32>(uint32{1}
+            << static_cast<uint32>(FMath::Clamp(L, 0, 8)));
         Lv.OriginCells = FIntVector(INT32_MAX, INT32_MAX, INT32_MAX);
         Lv.bHasData = false;
         Lv.Density.SetNumZeroed(Count);   // start all-air (0)
@@ -632,7 +635,8 @@ void UVoxelDensityVolume::ProcessOneFill(const FPendingFill& F)
     if (!Gen) return;
     if (bShuttingDown.load(std::memory_order_relaxed) || bFillThreadStop.load(std::memory_order_relaxed)) return;
 
-    const int32 Step = 1 << F.Level;
+    const int32 Step = static_cast<int32>(uint32{1}
+        << static_cast<uint32>(FMath::Clamp(F.Level, 0, 8)));
     FFillResult R;
     R.Level = F.Level;
     R.Epoch = F.Epoch;