fix: update PlateView fill path and sync stats with preview

- Route best-result updates to progress form preview in
  PlateView.FillWithProgress (Ctrl+F path) — was still using
  the old SetStationaryParts approach
- Only update results stats (parts, density, area) when
  IsOverallBest so they match the preview display

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

OpenNest/Controls/PlateView.cs

@@ -1243,15 +1243,24 @@ namespace OpenNest.Controls
             var cts = new CancellationTokenSource();
             var progressForm = new NestProgressForm(cts, showPlateRow: false);
 
+            var previewPlate = new Plate(Plate.Size)
+            {
+                Quadrant = Plate.Quadrant,
+                PartSpacing = Plate.PartSpacing,
+                Thickness = Plate.Thickness,
+                Material = Plate.Material,
+            };
+            previewPlate.EdgeSpacing = Plate.EdgeSpacing;
+            progressForm.PreviewPlate = previewPlate;
+
             var progress = new Progress<NestProgress>(p =>
             {
                 progressForm.UpdateProgress(p);
 
                 if (p.IsOverallBest)
-                    SetStationaryParts(p.BestParts);
+                    progressForm.UpdatePreview(p.BestParts);
-                else
-                    SetActiveParts(p.BestParts);
 
+                SetActiveParts(p.BestParts);
                 ActiveWorkArea = p.ActiveWorkArea;
             });
 

OpenNest/Forms/NestProgressForm.cs

@@ -71,17 +71,20 @@ namespace OpenNest.Forms
             }
 
             phaseStepper.ActivePhase = progress.Phase;
-
             SetValueWithFlash(plateValue, progress.PlateNumber.ToString());
-            SetValueWithFlash(partsValue, progress.BestPartCount.ToString());
 
-            var densityText = progress.BestDensity.ToString("P1");
+            if (progress.IsOverallBest)
-            var densityFlashColor = GetDensityColor(progress.BestDensity);
+            {
-            SetValueWithFlash(densityValue, densityText, densityFlashColor);
+                SetValueWithFlash(partsValue, progress.BestPartCount.ToString());
-            densityBar.Value = progress.BestDensity;
 
-            SetValueWithFlash(nestedAreaValue,
+                var densityText = progress.BestDensity.ToString("P1");
-                $"{progress.NestedWidth:F1} x {progress.NestedLength:F1} ({progress.NestedArea:F1} sq in)");
+                var densityFlashColor = GetDensityColor(progress.BestDensity);
+                SetValueWithFlash(densityValue, densityText, densityFlashColor);
+                densityBar.Value = progress.BestDensity;
+
+                SetValueWithFlash(nestedAreaValue,
+                    $"{progress.NestedWidth:F1} x {progress.NestedLength:F1} ({progress.NestedArea:F1} sq in)");
+            }
 
             descriptionValue.Text = !string.IsNullOrEmpty(progress.Description)
                 ? progress.Description