fix(data): leave the trailing empty plate out of nest record plate counts

The editor keeps an empty plate at the end of a nest as its new-plate slot.
Counting it made database records report one plate too many, so the record
now uses the same displayed-plate count as the UI.

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

OpenNest.Data/NestRecordFactory.cs

@@ -46,7 +46,8 @@ public static class NestRecordFactory
             Material = nest.Material?.Name ?? "",
             Thickness = nest.Thickness,
             Status = nest.Status,
-            PlateCount = nest.Plates.Count,
+            // The trailing empty plate is the editor's new-plate slot, not a plate of the nest.
+            PlateCount = PlateDisplayNumbering.DisplayedPlateCount(nest.Plates),
             PartCount = nest.Plates.Sum(CountNonCutoffParts),
             // Nest has no separate "comments" field; Notes is the closest analog
             // shown in the nest info dialog, so it round-trips as Comments here.

OpenNest.Tests/Data/NestRecordFactoryTests.cs

@@ -115,6 +115,21 @@ public class NestRecordFactoryTests
         Assert.Equal("", record.MadeBy);
     }
 
+    [Fact]
+    public void FromNest_TrailingEmptyPlate_NotCounted()
+    {
+        var nest = new Nest("Sentinel");
+        var drawing = new Drawing("A");
+        nest.Drawings.Add(drawing);
+        nest.CreatePlate().Parts.Add(new Part(drawing));
+        nest.CreatePlate();
+
+        var record = NestRecordFactory.FromNest(nest, Guid.NewGuid(), fileSize: 0);
+
+        Assert.Equal(1, record.PlateCount);
+        Assert.Equal(1, record.PartCount);
+    }
+
     [Fact]
     public void FromNest_PreservesGivenId()
     {