feat(ui): add bool checkbox support to ShapeLibraryForm

BuildParameterControls now creates a CheckBox (wired to UpdatePreview) for bool properties instead of a TextBox; CreateShapeFromInputs reads the Checked value via a short-circuit before the TextBox cast.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

OpenNest/Forms/ShapeLibraryForm.cs

@@ -180,6 +180,20 @@ namespace OpenNest.Forms
 
                 y += 18;
 
+                Control editor;
+                if (prop.PropertyType == typeof(bool))
+                {
+                    var cb = new CheckBox
+                    {
+                        Location = new Point(parametersPanel.Padding.Left, y),
+                        AutoSize = true,
+                        Checked = sourceValues != null && (bool)prop.GetValue(sourceValues)
+                    };
+                    cb.CheckedChanged += (s, ev) => UpdatePreview();
+                    editor = cb;
+                }
+                else
+                {
                     var tb = new TextBox
                     {
                         Location = new Point(parametersPanel.Padding.Left, y),
@@ -196,11 +210,13 @@ namespace OpenNest.Forms
                     }
 
                     tb.TextChanged += (s, ev) => UpdatePreview();
+                    editor = tb;
+                }
 
-                parameterBindings.Add(new ParameterBinding { Property = prop, Control = tb });
+                parameterBindings.Add(new ParameterBinding { Property = prop, Control = editor });
 
                 parametersPanel.Controls.Add(label);
-                parametersPanel.Controls.Add(tb);
+                parametersPanel.Controls.Add(editor);
 
                 y += 30;
             }
@@ -241,6 +257,13 @@ namespace OpenNest.Forms
 
             foreach (var binding in parameterBindings)
             {
+                if (binding.Property.PropertyType == typeof(bool))
+                {
+                    var cb = (CheckBox)binding.Control;
+                    binding.Property.SetValue(shape, cb.Checked);
+                    continue;
+                }
+
                 var tb = (TextBox)binding.Control;
 
                 if (binding.Property.PropertyType == typeof(int))