fix(autonest): show part rotation limits in degrees

The Rot Start, Rot End and Step columns showed the drawing's radian
constraints as-is, so users had to type 1.5708 for 90 degrees. The grid now
shows and accepts degrees; rows keep the radian values, so an unedited row
passes the drawing's limits to the engine without a conversion round trip.

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

OpenNest.WinForms.Tests/Forms/AutoNestFormRotationTests.cs

@@ -0,0 +1,53 @@
+using System.Windows.Forms;
+using OpenNest.CNC;
+using OpenNest.Forms;
+
+namespace OpenNest.WinForms.Tests.Forms;
+
+public class AutoNestFormRotationTests
+{
+    [Fact]
+    public void RotationColumnsShowDegreesAndNestItemsKeepRadians()
+    {
+        RunSta(() =>
+        {
+            var drawing = new Drawing("grain", new Program()) { Quantity = { Required = 2 } };
+            drawing.Constraints.StartAngle = 0;
+            drawing.Constraints.EndAngle = System.Math.PI / 2;
+            drawing.Constraints.StepAngle = System.Math.PI / 2;
+            var nest = new Nest();
+            nest.Drawings.Add(drawing);
+
+            using var form = new AutoNestForm(nest);
+            var grid = GetGrid(form);
+            Assert.Equal(0.0, grid.Rows[0].Cells[Column(grid, "RotationStart")].Value);
+            Assert.Equal(90.0, grid.Rows[0].Cells[Column(grid, "RotationEnd")].Value);
+            Assert.Equal(90.0, grid.Rows[0].Cells[Column(grid, "StepAngle")].Value);
+
+            var item = Assert.Single(form.GetNestItems());
+            Assert.Equal(System.Math.PI / 2, item.RotationEnd);
+            Assert.Equal(System.Math.PI / 2, item.StepAngle);
+
+            grid.Rows[0].Cells[Column(grid, "RotationEnd")].Value = 180.0;
+            grid.Rows[0].Cells[Column(grid, "StepAngle")].Value = 45.0;
+            item = Assert.Single(form.GetNestItems());
+            Assert.Equal(System.Math.PI, item.RotationEnd, 12);
+            Assert.Equal(System.Math.PI / 4, item.StepAngle, 12);
+        });
+    }
+
+    private static DataGridView GetGrid(AutoNestForm form)
+    {
+        // Binding needs a context even when the test does not show the form.
+        form.BindingContext = new BindingContext();
+        var grid = Assert.IsType<DataGridView>(form.Controls.Find("partsGrid", true).Single());
+        grid.CreateControl();
+        return grid;
+    }
+
+    private static int Column(DataGridView grid, string property) =>
+        grid.Columns.Cast<DataGridViewColumn>().Single(c => c.DataPropertyName == property).Index;
+
+    private static void RunSta(Action action) =>
+        StaTestThread.Run(action, TimeSpan.FromSeconds(15), "The STA test did not complete.");
+}

OpenNest/Forms/AutoNestForm.cs

@@ -11,6 +11,7 @@ using OpenNest.Data.MaterialLedger;
 using OpenNest.Engine;
 using OpenNest.Geometry;
 using OpenNest.Help;
+using OpenNest.Math;
 
 namespace OpenNest.Forms
 {
@@ -257,9 +258,9 @@ namespace OpenNest.Forms
                 nestItem.Drawing = gridItem.RefDrawing;
                 nestItem.Priority = gridItem.Priority;
                 nestItem.Quantity = gridItem.Quantity;
-                nestItem.RotationEnd = gridItem.RotationEnd;
-                nestItem.RotationStart = gridItem.RotationStart;
-                nestItem.StepAngle = gridItem.StepAngle;
+                nestItem.RotationEnd = gridItem.RotationEndRadians;
+                nestItem.RotationStart = gridItem.RotationStartRadians;
+                nestItem.StepAngle = gridItem.StepAngleRadians;
 
                 nestItems.Add(nestItem);
             }
@@ -880,9 +881,9 @@ namespace OpenNest.Forms
             item.RefDrawing = dwg;
             item.Quantity = dwg.Quantity.Remaining > 0 ? dwg.Quantity.Remaining : 0;
             item.Priority = dwg.Priority;
-            item.RotationStart = dwg.Constraints.StartAngle;
-            item.RotationEnd = dwg.Constraints.EndAngle;
-            item.StepAngle = dwg.Constraints.StepAngle;
+            item.RotationStartRadians = dwg.Constraints.StartAngle;
+            item.RotationEndRadians = dwg.Constraints.EndAngle;
+            item.StepAngleRadians = dwg.Constraints.StepAngle;
 
             return item;
         }
@@ -903,14 +904,35 @@ namespace OpenNest.Forms
 
             public int Priority { get; set; }
 
+            // Rotations are kept in radians and shown in degrees, so an unedited row passes
+            // the drawing's limits through without a conversion round trip.
+            internal double RotationStartRadians { get; set; }
+            internal double RotationEndRadians { get; set; }
+            internal double StepAngleRadians { get; set; }
+
             [DisplayName("Rot Start")]
-            public double RotationStart { get; set; }
+            public double RotationStart
+            {
+                get => ToDisplayDegrees(RotationStartRadians);
+                set => RotationStartRadians = Angle.ToRadians(value);
+            }
 
             [DisplayName("Rot End")]
-            public double RotationEnd { get; set; }
+            public double RotationEnd
+            {
+                get => ToDisplayDegrees(RotationEndRadians);
+                set => RotationEndRadians = Angle.ToRadians(value);
+            }
 
             [DisplayName("Step")]
-            public double StepAngle { get; set; }
+            public double StepAngle
+            {
+                get => ToDisplayDegrees(StepAngleRadians);
+                set => StepAngleRadians = Angle.ToRadians(value);
+            }
+
+            private static double ToDisplayDegrees(double radians) =>
+                System.Math.Round(Angle.ToDegrees(radians), 4);
         }
 
         private class PlateOptionItem