feat(machine-config): name blank standard thicknesses on open

Thicknesses saved before the auto-fill kept a blank Name / Gauge until someone
edited their value, so their nest reports showed only the decimal. Opening
Machine Configuration now names every blank thickness that matches a standard
gauge or plate fraction and marks the form changed, so closing offers to save
them. Thicknesses matching none stay blank, and once saved a reopen finds
nothing to fill and does not ask again.

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

OpenNest.WinForms.Tests/Forms/MachineCutsFormsTests.cs

@@ -182,6 +182,64 @@ public class MachineCutsFormsTests
         });
     }
 
+    [Fact]
+    public void Opening_NamesBlankStandardThicknessesAndOffersToSaveThem()
+    {
+        RunSta(() =>
+        {
+            var directory = Path.Combine(Path.GetTempPath(), "OpenNestTests", Guid.NewGuid().ToString());
+            Directory.CreateDirectory(directory);
+            try
+            {
+                var provider = new LocalJsonProvider(directory);
+                provider.SaveMachine(new MachineConfig
+                {
+                    Name = "Laser",
+                    Units = UnitSystem.Inches,
+                    Materials =
+                    {
+                        new MaterialConfig
+                        {
+                            Name = "Mild Steel",
+                            Thicknesses =
+                            {
+                                new ThicknessConfig { Value = 0.25 },
+                                new ThicknessConfig { Value = 0.0598, Name = "Shop sheet" },
+                                new ThicknessConfig { Value = 0.3 },
+                            },
+                        },
+                    },
+                });
+
+                using (var form = new MachineConfigForm(provider))
+                {
+                    var names = Descendants(Find<TreeView>(form, "_tree").Nodes)
+                        .Where(n => n.Tag is ThicknessConfig).Select(n => n.Text).ToList();
+                    Assert.Equal(new[] { "0.25 (1/4\")", "0.0598 (Shop sheet)", "0.3" }, names);
+                    Assert.True(Dirty(form));
+                }
+
+                // Closed without saving, so the file is still blank; once the names are saved,
+                // opening again finds nothing to name and changes nothing.
+                var saved = provider.GetMachine(provider.GetMachines().Single().Id)!;
+                Assert.True(MachineConfigForm.FillBlankThicknessNames(saved));
+                provider.SaveMachine(saved);
+                Assert.Equal("1/4\"", provider.GetMachine(saved.Id)!.Materials[0].Thicknesses[0].Name);
+                using (var reopened = new MachineConfigForm(provider))
+                    Assert.False(Dirty(reopened));
+            }
+            finally
+            {
+                Directory.Delete(directory, recursive: true);
+            }
+        });
+    }
+
+    private static bool Dirty(MachineConfigForm form) =>
+        (bool)typeof(MachineConfigForm)
+            .GetField("_dirty", System.Reflection.BindingFlags.Instance | System.Reflection.BindingFlags.NonPublic)!
+            .GetValue(form)!;
+
     private static IEnumerable<TreeNode> Descendants(TreeNodeCollection nodes) =>
         nodes.Cast<TreeNode>().SelectMany(n => Descendants(n.Nodes).Prepend(n));
 

OpenNest/Forms/MachineConfigForm.cs

@@ -81,6 +81,10 @@ namespace OpenNest.Forms
                 if (machine is null)
                     continue;
 
+                // Blank names get their standard gauge or fraction now, so the tree and nest
+                // reports show them; closing then offers to save what was filled.
+                if (FillBlankThicknessNames(machine))
+                    MarkDirty();
                 _tree.Nodes.Add(BuildMachineNode(machine));
             }
 
@@ -1176,11 +1180,34 @@ namespace OpenNest.Forms
         /// matches, such as "16 ga" or "1/4\"", or empty when it matches none.
         /// </summary>
         private string StandardThicknessName(double value) =>
+            StandardThicknessName(value, _currentMachine?.Units ?? UnitSystem.Inches);
+
+        private static string StandardThicknessName(double value, UnitSystem units) =>
             StandardThicknesses.Find(
                 value,
-                _currentMachine?.Units == UnitSystem.Millimeters ? Units.Millimeters : Units.Inches
+                units == UnitSystem.Millimeters ? Units.Millimeters : Units.Inches
             )?.Name ?? "";
 
+        /// <summary>
+        /// Names every unnamed thickness of <paramref name="machine"/> that matches a standard
+        /// gauge or plate fraction; true when it named any.
+        /// </summary>
+        internal static bool FillBlankThicknessNames(MachineConfig machine)
+        {
+            var filled = false;
+            foreach (var thickness in machine.Materials.SelectMany(m => m.Thicknesses))
+            {
+                if (!string.IsNullOrWhiteSpace(thickness.Name))
+                    continue;
+                var name = StandardThicknessName(thickness.Value, machine.Units);
+                if (name.Length == 0)
+                    continue;
+                thickness.Name = name;
+                filled = true;
+            }
+            return filled;
+        }
+
         private string LengthUnitSuffix(object _) =>
             _currentMachine?.Units == UnitSystem.Millimeters ? "mm" : "in";
 

docs/machine-cutting-defaults.md

@@ -19,7 +19,9 @@ A thickness's **Name / Gauge** ("16 ga") is display only: the tree shows it and
 put it before the decimal. In Machine Configuration a blank name, or one still the standard
 name of the old value, follows the thickness value to its standard steel gauge or plate
 fraction (`StandardThicknesses`, matched to the displayed precision); a typed name is kept.
-A new thickness starts with the name of its default value.
+A new thickness starts with the name of its default value. Opening Machine Configuration
+names every blank thickness that matches a standard one and, when it named any, offers to
+save them on close; thicknesses matching none stay blank.
 
 ## Where the Cutting Parameters dialog saves