fix: correct Size width/length ordering and add CLI docs to README

Size.Parse and ToString now use WxL format (width first) matching the
natural convention. Fixed the Plate(w,l) constructor which was swapping
args when creating Size. Fixed PlateView.DrawPlate and DrawControl
ZoomToArea which had width/length mapped to the wrong screen axes.

Simplified Console --size parsing to use Size.TryParse instead of manual
split with confusing PlateHeight/PlateWidth fields. Added Command-Line
Interface section to README documenting all console options.

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

OpenNest.Core/Geometry/Size.cs

@@ -6,14 +6,14 @@ namespace OpenNest.Geometry
     {
         public Size(double width, double length)
         {
-            Length = length;
             Width = width;
+            Length = length;
         }
 
-        public double Length;
-
         public double Width;
 
+        public double Length;
+
         public static Size Parse(string size)
         {
             var a = size.ToUpper().Split('X');
@@ -21,8 +21,8 @@ namespace OpenNest.Geometry
             if (a.Length > 2)
                 throw new FormatException("Invalid size format.");
 
-            var length = double.Parse(a[0]);
-            var width = double.Parse(a[1]);
+            var width = double.Parse(a[0]);
+            var length = double.Parse(a[1]);
 
             return new Size(width, length);
         }
@@ -42,14 +42,8 @@ namespace OpenNest.Geometry
             return true;
         }
 
-        public override string ToString()
-        {
-            return string.Format("{0} x {1}", Length, Width);
-        }
-
-        public string ToString(int decimalPlaces)
-        {
-            return string.Format("{0} x {1}", System.Math.Round(Length, decimalPlaces), System.Math.Round(Width, decimalPlaces));
-        }
+        public override string ToString() => $"{Width} x {Length}";
+        
+        public string ToString(int decimalPlaces) => $"{System.Math.Round(Width, decimalPlaces)} x {System.Math.Round(Length, decimalPlaces)}";
     }
 }

OpenNest.Core/Plate.cs

@@ -35,7 +35,7 @@ namespace OpenNest
         }
 
         public Plate(double width, double length)
-            : this(new Size(length, width))
+            : this(new Size(width, length))
         {
         }