feat: add UpdatePreview method and PreviewPlate property

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

OpenNest/Forms/NestProgressForm.cs

@@ -27,11 +27,23 @@ namespace OpenNest.Forms
 
         public bool Accepted { get; private set; }
 
+        public Plate PreviewPlate
+        {
+            get => previewPlateView.Plate;
+            set
+            {
+                previewPlateView.Plate = value;
+                previewPlateView.ZoomToFit();
+            }
+        }
+
         public NestProgressForm(CancellationTokenSource cts, bool showPlateRow = true)
         {
             this.cts = cts;
             InitializeComponent();
 
+            previewPlateView.AllowSelect = false;
+
             if (!showPlateRow)
             {
                 plateLabel.Visible = false;
@@ -76,6 +88,20 @@ namespace OpenNest.Forms
                 : progress.Phase.DisplayName();
         }
 
+        public void UpdatePreview(List<Part> bestParts)
+        {
+            if (IsDisposed || !IsHandleCreated)
+                return;
+
+            var plate = previewPlateView.Plate;
+            plate.Parts.Clear();
+
+            foreach (var part in bestParts)
+                plate.Parts.Add((Part)part.Clone());
+
+            previewPlateView.ZoomToFit();
+        }
+
         public void ShowCompleted()
         {
             if (IsDisposed || !IsHandleCreated)
@@ -135,6 +161,8 @@ namespace OpenNest.Forms
             if (!cts.IsCancellationRequested)
                 cts.Cancel();
 
+            previewPlateView.Dispose();
+
             base.OnFormClosing(e);
         }