fix: set bend line entity color to ByLayer

Bend lines retained their original explicit color (white) from
SolidWorks after being moved to the BEND layer. Now set to ByLayer
so they inherit the layer's yellow color.

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

EtchBendLines/Etcher.cs

@@ -100,10 +100,11 @@ namespace EtchBendLines
             var doc = LoadDocument(filePath);
             var bends = ExtractBends(doc);
 
-            // Ensure all bend lines are on the BEND layer
+            // Ensure all bend lines are on the BEND layer with ByLayer color
             foreach (var bend in bends)
             {
                 bend.Line.Layer = BendLayer;
+                bend.Line.Color = Color.ByLayer;
             }
 
             var upBends = bends.Where(b => b.Direction == BendDirection.Up);