fix(engine): canonicalize PlaceBestFitPairs builds to match BestFitCache frame

OpenNest.Engine/NestEngineBase.cs

@@ -334,6 +334,12 @@ namespace OpenNest
                 var bestFits = BestFitCache.GetOrCompute(
                     item.Drawing, Plate.Size.Length, Plate.Size.Width, Plate.PartSpacing);
 
+                // BestFitCache stores pair coordinates in canonical frame. Build candidates
+                // from a canonical drawing copy so geometry and coords share a frame; rebind
+                // + un-rotate winning pair to the original drawing's frame before returning.
+                var canonicalDrawing = CanonicalFrame.AsCanonicalCopy(item.Drawing);
+                var sourceAngle = item.Drawing?.Source?.Angle ?? 0.0;
+
                 List<Part> bestPlacement = null;
                 Box bestTarget = null;
 
@@ -342,7 +348,7 @@ namespace OpenNest
                     if (!fit.Keep)
                         continue;
 
-                    var parts = fit.BuildParts(item.Drawing);
+                    var parts = fit.BuildParts(canonicalDrawing);
                     var pairBbox = ((IEnumerable<IBoundable>)parts).GetBoundingBox();
                     var pairW = pairBbox.Width;
                     var pairL = pairBbox.Length;
@@ -374,6 +380,10 @@ namespace OpenNest
 
                 if (bestPlacement == null) continue;
 
+                // Rebind to the original drawing and compose sourceAngle onto rotation so the
+                // final placed parts sit in the user's visible frame.
+                bestPlacement = RebindPairToOriginal(bestPlacement, item.Drawing, sourceAngle);
+
                 result.AddRange(bestPlacement);
                 item.Quantity = 0;
 
@@ -388,6 +398,30 @@ namespace OpenNest
             return result;
         }
 
+        /// <summary>
+        /// Rebinds each canonical-frame Part in the pair to the original Drawing at its current
+        /// world pose, then composes sourceAngle onto each via CanonicalFrame.FromCanonical so
+        /// the returned list is in the original drawing's visible frame. Mirrors
+        /// DefaultNestEngine.RebindAndUnCanonicalize.
+        /// </summary>
+        private static List<Part> RebindPairToOriginal(List<Part> parts, Drawing original, double sourceAngle)
+        {
+            if (parts == null || parts.Count == 0)
+                return parts;
+
+            for (var i = 0; i < parts.Count; i++)
+            {
+                var p = parts[i];
+                var rebound = Part.CreateAtOrigin(original, p.Rotation);
+                var delta = p.BoundingBox.Location - rebound.BoundingBox.Location;
+                rebound.Offset(delta);
+                rebound.UpdateBounds();
+                parts[i] = rebound;
+            }
+
+            return CanonicalFrame.FromCanonical(parts, sourceAngle);
+        }
+
         /// <summary>
         /// Determines whether a drawing should use grid-fill (true) or bin-pack (false).
         /// Low-quantity items whose total area is a small fraction of the plate are