fix(ui): scale the fill time in the status bar

Long fills read as thousands of milliseconds. Keep milliseconds under
a second, then show seconds and minutes so the time stays readable.

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

OpenNest.WinForms.Tests/Controls/PlateViewFillTimeTests.cs

@@ -0,0 +1,18 @@
+using OpenNest.Controls;
+
+namespace OpenNest.WinForms.Tests.Controls;
+
+public class PlateViewFillTimeTests
+{
+    [Theory]
+    [InlineData(0, "0 ms")]
+    [InlineData(850, "850 ms")]
+    [InlineData(999, "999 ms")]
+    [InlineData(1000, "1.0 s")]
+    [InlineData(2400, "2.4 s")]
+    [InlineData(59960, "59.9 s")]
+    [InlineData(60000, "1m 00s")]
+    [InlineData(125000, "2m 05s")]
+    public void FillTimeIsShownInTheLargestUnitThatFits(int milliseconds, string expected) =>
+        Assert.Equal(expected, PlateView.FormatFillTime(TimeSpan.FromMilliseconds(milliseconds)));
+}

OpenNest/Controls/PlateView.cs

@@ -995,7 +995,7 @@ namespace OpenNest.Controls
                         change.Complete();
 
                         sw.Stop();
-                        Status = $"Fill: {parts.Count} parts in {sw.ElapsedMilliseconds} ms";
+                        Status = $"Fill: {parts.Count} parts in {FormatFillTime(sw.Elapsed)}";
                     }
                     else
                     {
@@ -1023,6 +1023,18 @@ namespace OpenNest.Controls
             }
         }
 
+        // Truncates so a time just under a unit boundary never reads as "60.0 s".
+        internal static string FormatFillTime(TimeSpan elapsed)
+        {
+            if (elapsed.TotalSeconds < 1)
+                return $"{(int)elapsed.TotalMilliseconds} ms";
+
+            if (elapsed.TotalMinutes < 1)
+                return $"{(int)(elapsed.TotalSeconds * 10) / 10.0:0.0} s";
+
+            return $"{(int)elapsed.TotalMinutes}m {elapsed.Seconds:00}s";
+        }
+
         public void RemoveSelectedParts() => selection.RemoveSelectedParts();
 
         private void redrawTimer_Elapsed(object sender, System.Timers.ElapsedEventArgs e)