feat(shapes): generate unique drawing names from parameters and add toolbar button

Shape library drawings now get descriptive names based on their
parameters (e.g. "Rectangle 12x6", "Circle 8 Dia") instead of generic
type names, preventing silent duplicates in the DrawingCollection
HashSet. Added a Shape Library button to the Drawings tab toolbar
and removed separators between toolbar buttons for a cleaner look.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

OpenNest.Core/Shapes/ShapeDefinition.cs

@@ -26,6 +26,14 @@ namespace OpenNest.Shapes
 
         public abstract Drawing GetDrawing();
 
+        public virtual string GenerateName()
+        {
+            var typeName = GetType().Name;
+            return typeName.EndsWith("Shape")
+                ? typeName.Substring(0, typeName.Length - 5)
+                : typeName;
+        }
+
         public virtual void SetPreviewDefaults() { }
 
         public static List<T> LoadFromJson<T>(string path) where T : ShapeDefinition
@@ -34,6 +42,8 @@ namespace OpenNest.Shapes
             return JsonSerializer.Deserialize<List<T>>(json, JsonOptions);
         }
 
+        protected static string Dim(double value) => value.ToString("0.###");
+
         protected Drawing CreateDrawing(List<Entity> entities)
         {
             var pgm = ConvertGeometry.ToProgram(entities);