Mesh Optimizer: sibling StaticMesh duplicate remover (UE 5.7)

Editor plugin that detects geometrically-identical sibling StaticMeshes across a
level, rebases each placement onto one canonical mesh with a corrected transform
(W' = D * W, verified by exact vertex matching), and can collapse groups into HISM.
Native Slate tool panel + BlueprintCallable UOptimizerSubsystem.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

Source/OptimizerEditor/Private/OptimizerReconciler.cpp

@@ -0,0 +1,40 @@
+// Copyright IHY.
+#include "OptimizerReconciler.h"
+
+namespace OptimizerReconciler
+{
+	bool ComputeCorrectedWorld(
+		const FMatrix& CanonToMember,
+		const FTransform& W,
+		const FBox& CanonLocalBounds,
+		double ShearTol,
+		FTransform& OutWprime,
+		double& OutMaxCornerDev)
+	{
+		// Exact corrected world matrix: apply D first (canon-local -> sibling-local), then W.
+		const FMatrix Exact = CanonToMember * W.ToMatrixWithScale();
+		OutWprime.SetFromMatrix(Exact);
+
+		// Compare the FTransform reconstruction against the exact matrix at the canonical bbox corners.
+		// Any gap means the exact matrix had shear that FTransform discarded -> not representable.
+		const FVector Mn = CanonLocalBounds.Min;
+		const FVector Mx = CanonLocalBounds.Max;
+		const FVector Corners[8] =
+		{
+			FVector(Mn.X, Mn.Y, Mn.Z), FVector(Mx.X, Mn.Y, Mn.Z),
+			FVector(Mn.X, Mx.Y, Mn.Z), FVector(Mx.X, Mx.Y, Mn.Z),
+			FVector(Mn.X, Mn.Y, Mx.Z), FVector(Mx.X, Mn.Y, Mx.Z),
+			FVector(Mn.X, Mx.Y, Mx.Z), FVector(Mx.X, Mx.Y, Mx.Z)
+		};
+
+		double MaxDev = 0.0;
+		for (const FVector& C : Corners)
+		{
+			const FVector ExactPt = Exact.TransformPosition(C);
+			const FVector ViaTransform = OutWprime.TransformPosition(C);
+			MaxDev = FMath::Max(MaxDev, FVector::Dist(ExactPt, ViaTransform));
+		}
+		OutMaxCornerDev = MaxDev;
+		return MaxDev <= ShearTol;
+	}
+}