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/PipeFlangeShape.cs

@@ -13,6 +13,14 @@ namespace OpenNest.Shapes
         public double PipeClearance { get; set; }
         public bool Blind { get; set; }
 
+        public override string GenerateName()
+        {
+            var name = $"Pipe Flange {Dim(OD)} OD";
+            if (!string.IsNullOrEmpty(PipeSize))
+                name += $" {PipeSize} Pipe";
+            return name;
+        }
+
         public override void SetPreviewDefaults()
         {
             OD = 7.5;