fix: fill preview now matches accepted layout

Refresh PlateView preview with settled parts after Compactor.Settle
so the accepted layout matches what was shown, not the pre-settle
positions from the last progress report.

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

OpenNest/Controls/PlateView.cs

@@ -1279,6 +1279,7 @@ namespace OpenNest.Controls
 
                 if (parts.Count > 0 && (!cts.IsCancellationRequested || progressForm.Accepted))
                 {
+                    SetActiveParts(parts);
                     AcceptPreviewParts(parts);
 
                     if (Plate.CutOffs.Count > 0)