fix(ui): stop the cut simulator's time readout flashing

Playback rewrites the status labels every frame, and a plain Label erases
its background before drawing the new text, so the time blinked. The status
values now use a double-buffered label.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

OpenNest/Forms/CutSimulatorForm.cs

@@ -225,7 +225,7 @@ namespace OpenNest.Forms
 
         // Fixed height so changing text never resizes the window.
         private Label StatusValue(int lines) =>
-            new()
+            new BufferedLabel
             {
                 AutoSize = false,
                 AutoEllipsis = true,
@@ -451,5 +451,14 @@ namespace OpenNest.Forms
 
             base.OnFormClosed(e);
         }
+
+        // Playback rewrites the status every frame; a plain label erases before it redraws, so it flashes.
+        private sealed class BufferedLabel : Label
+        {
+            public BufferedLabel()
+            {
+                DoubleBuffered = true;
+            }
+        }
     }
 }