refactor: move CutParameters to OpenNest.Api namespace with new properties

Relocates CutParameters from OpenNest namespace to OpenNest.Api, adds
LeadInLength and PostProcessor properties, and provides a typed Default
factory. Updates Timing.cs, the WinForms project reference, and the three
consuming forms to resolve the type from the new namespace.

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

OpenNest.Core/CutParameters.cs

@@ -1,15 +1,21 @@
-using System;
+using System;
 
-namespace OpenNest
+namespace OpenNest.Api;
+
+public class CutParameters
 {
-    public class CutParameters
+    public double Feedrate { get; set; }
+    public double RapidTravelRate { get; set; }
+    public TimeSpan PierceTime { get; set; }
+    public double LeadInLength { get; set; }
+    public string PostProcessor { get; set; }
+    public Units Units { get; set; }
+
+    public static CutParameters Default => new()
     {
-        public double Feedrate { get; set; }
-
-        public double RapidTravelRate { get; set; }
-
-        public TimeSpan PierceTime { get; set; }
-
-        public Units Units { get; set; }
-    }
+        Feedrate = 100,
+        RapidTravelRate = 300,
+        PierceTime = TimeSpan.FromSeconds(0.5),
+        Units = OpenNest.Units.Inches
+    };
 }

OpenNest.Core/Timing.cs

@@ -1,5 +1,6 @@
 using System;
 using System.Linq;
+using OpenNest.Api;
 using OpenNest.CNC;
 using OpenNest.Converters;
 using OpenNest.Geometry;