feat: add Assign Lead-ins button to EditNestForm toolbar

Adds a text-only toolbar button to the Plates tab that opens the
CuttingParametersForm, saves the chosen parameters on the plate, and
runs LeadInAssigner with LeftSideSequencer to auto-assign lead-ins.

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

OpenNest/Forms/EditNestForm.Designer.cs

@@ -38,6 +38,7 @@
             this.qtyColumn = ((System.Windows.Forms.ColumnHeader)(new System.Windows.Forms.ColumnHeader()));
             this.toolStrip1 = new System.Windows.Forms.ToolStrip();
             this.toolStripButton1 = new System.Windows.Forms.ToolStripButton();
+            this.btnAssignLeadIns = new System.Windows.Forms.ToolStripButton();
             this.tabPage2 = new System.Windows.Forms.TabPage();
             this.drawingListBox1 = new OpenNest.Controls.DrawingListBox();
             this.toolStrip2 = new System.Windows.Forms.ToolStrip();
@@ -133,7 +134,8 @@
             this.toolStrip1.GripStyle = System.Windows.Forms.ToolStripGripStyle.Hidden;
             this.toolStrip1.ImageScalingSize = new System.Drawing.Size(20, 20);
             this.toolStrip1.Items.AddRange(new System.Windows.Forms.ToolStripItem[] {
-            this.toolStripButton1});
+            this.toolStripButton1,
+            this.btnAssignLeadIns});
             this.toolStrip1.Location = new System.Drawing.Point(3, 3);
             this.toolStrip1.Name = "toolStrip1";
             this.toolStrip1.Size = new System.Drawing.Size(227, 31);
@@ -152,6 +154,15 @@
             this.toolStripButton1.Text = "Calculate Cut Time";
             this.toolStripButton1.Click += new System.EventHandler(this.CalculateSelectedPlateCutTime_Click);
             //
+            // btnAssignLeadIns
+            //
+            this.btnAssignLeadIns.DisplayStyle = System.Windows.Forms.ToolStripItemDisplayStyle.Text;
+            this.btnAssignLeadIns.ImageTransparentColor = System.Drawing.Color.Magenta;
+            this.btnAssignLeadIns.Name = "btnAssignLeadIns";
+            this.btnAssignLeadIns.Size = new System.Drawing.Size(96, 28);
+            this.btnAssignLeadIns.Text = "Assign Lead-ins";
+            this.btnAssignLeadIns.Click += new System.EventHandler(this.AssignLeadIns_Click);
+            //
             // tabPage2
             // 
             this.tabPage2.Controls.Add(this.drawingListBox1);
@@ -266,5 +277,6 @@
         private System.Windows.Forms.ToolStripButton toolStripButton2;
         private System.Windows.Forms.ToolStripSeparator toolStripSeparator1;
         private System.Windows.Forms.ToolStripButton toolStripButton3;
+        private System.Windows.Forms.ToolStripButton btnAssignLeadIns;
     }
 }

OpenNest/Forms/EditNestForm.cs

@@ -2,6 +2,7 @@
 using OpenNest.CNC.CuttingStrategy;
 using OpenNest.Collections;
 using OpenNest.Controls;
+using OpenNest.Engine;
 using OpenNest.Engine.Sequencing;
 using OpenNest.IO;
 using OpenNest.Math;
@@ -711,6 +712,32 @@ namespace OpenNest.Forms
             CalculateCurrentPlateCutTime();
         }
 
+        private void AssignLeadIns_Click(object sender, EventArgs e)
+        {
+            if (PlateView?.Plate == null)
+                return;
+
+            var plate = PlateView.Plate;
+
+            using var form = new CuttingParametersForm();
+            if (plate.CuttingParameters != null)
+                form.Parameters = plate.CuttingParameters;
+
+            if (form.ShowDialog(this) != DialogResult.OK)
+                return;
+
+            var parameters = form.BuildParameters();
+            plate.CuttingParameters = parameters;
+
+            var assigner = new LeadInAssigner
+            {
+                Sequencer = new LeftSideSequencer()
+            };
+            assigner.Assign(plate);
+
+            PlateView.Invalidate();
+        }
+
         private void ImportDrawings_Click(object sender, EventArgs e)
         {
             Import();