feat(ui): add nested dimensions and area to progress window

Show width x length and total part area on the "Nested:" row
in the nesting progress dialog, using the existing GetBoundingBox
extension to compute the extents.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

OpenNest.Engine/NestEngine.cs

@@ -723,12 +723,17 @@ namespace OpenNest
                 totalPartArea += part.BaseDrawing.Area;
             }
 
+            var bounds = best.GetBoundingBox();
+
             progress.Report(new NestProgress
             {
                 Phase = phase,
                 PlateNumber = plateNumber,
                 BestPartCount = score.Count,
                 BestDensity = score.Density,
+                NestedWidth = bounds.Width,
+                NestedLength = bounds.Length,
+                NestedArea = totalPartArea,
                 UsableRemnantArea = workArea.Area() - totalPartArea,
                 BestParts = clonedParts,
                 Description = description

OpenNest.Engine/NestProgress.cs

@@ -37,6 +37,9 @@ namespace OpenNest
         public int PlateNumber { get; set; }
         public int BestPartCount { get; set; }
         public double BestDensity { get; set; }
+        public double NestedWidth { get; set; }
+        public double NestedLength { get; set; }
+        public double NestedArea { get; set; }
         public double UsableRemnantArea { get; set; }
         public List<Part> BestParts { get; set; }
         public string Description { get; set; }