feat: add pierce point visualization and rename shape dimensions to Length/Width

Add toggleable pierce point drawing to PlateView that shows small red
filled circles at each rapid move endpoint (where cutting begins). Wire
through View menu, EditNestForm toggle, and MainForm handler.

Also rename RectangleShape/RoundedRectangleShape Width/Height to
Length/Width for consistency with CNC conventions, update MCP tools and
tests accordingly. Fix SplitDrawingForm designer layout ordering and
EntityView bend line selection styling.

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

OpenNest.Mcp/Tools/SetupTools.cs

@@ -19,13 +19,13 @@ namespace OpenNest.Mcp.Tools
         [Description("Create a new plate with the given dimensions and spacing. Returns plate index and work area.")]
         public string CreatePlate(
             [Description("Plate width")] double width,
-            [Description("Plate height")] double height,
+            [Description("Plate length")] double length,
             [Description("Spacing between parts (default 0)")] double partSpacing = 0,
             [Description("Edge spacing on all sides (default 0)")] double edgeSpacing = 0,
             [Description("Quadrant 1-4 (default 1). 1=TopRight, 2=TopLeft, 3=BottomLeft, 4=BottomRight")] int quadrant = 1,
             [Description("Material name (optional)")] string material = null)
         {
-            var plate = new Plate(width, height);
+            var plate = new Plate(width, length);
             plate.PartSpacing = partSpacing;
             plate.EdgeSpacing = new Spacing(edgeSpacing, edgeSpacing);
             plate.Quadrant = quadrant;