refactor(PepLib.Core): move Node classes to Utilities namespace

Node and KeyNode are INI parsing helpers used by IniConfig,
not geometry types. Move from Geometry/ to Utilities/.

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

PepLib.Core/Geometry/Node.cs

@@ -1,82 +0,0 @@
-namespace PepLib.Geometry
-{
-    public class Node
-    {
-        private Node parent;
-
-        public List<Node> Children;
-
-        public Node()
-        {
-            Children = new List<Node>();
-        }
-
-        public Node Parent
-        {
-            get { return parent; }
-            set
-            {
-                parent = value;
-                UpdateDepth();
-            }
-        }
-
-        public string Value { get; set; }
-
-        private void UpdateDepth()
-        {
-            if (Parent != null)
-                Level = Parent.Level + 1;
-            else
-                Level = 0;
-
-            foreach (var node in Children)
-                node.Parent = this;
-        }
-
-        public int Level { get; protected set; }
-
-        public void AddChild(Node node)
-        {
-            node.Parent = this;
-            Children.Add(node);
-        }
-
-        public void Write(TextWriter writer)
-        {
-            writer.WriteLine("".PadLeft(Level * 2) + this.ToString());
-
-            foreach (var node in Children)
-                node.Write(writer);
-        }
-
-        public override string ToString()
-        {
-            return Value;
-        }
-    }
-
-    public class KeyNode : Node
-    {
-        public string Name;
-
-        public static KeyNode Parse(Node node)
-        {
-            var index = node.Value.IndexOf('=');
-
-            if (index == -1)
-                return null;
-
-            return new KeyNode()
-            {
-                Name = node.Value.Remove(index),
-                Value = node.Value.Remove(0, index + 1).Trim()
-            };
-        }
-
-        public override string ToString()
-        {
-            return string.Format("{0}={1}", Name, Value);
-        }
-    }
-}