Rename because it is ordered

PersistentOrderedMap/PersistentOrderedMap.cs

@@ -0,0 +1,44 @@
+using System.Collections;
+
+namespace PersistentOrderedMap;
+
+public sealed class PersistentOrderedMap<K, V, TStrategy> : BaseOrderedMap<K, V, TStrategy>, IEnumerable, IEnumerable<KeyValuePair<K, V>> where TStrategy : IKeyStrategy<K>
+{
+    internal PersistentOrderedMap(Node<K> root, TStrategy strategy, int count) 
+        : base(root, strategy, count) { }
+
+    // ---------------------------------------------------------
+    // Immutable Write API (Returns new Map)
+    // ---------------------------------------------------------
+    public PersistentOrderedMap<K, V, TStrategy> Set(K key, V value)
+    {
+        // OPTIMIZATION: Use OwnerId.None (0).
+        // This signals EnsureEditable to always copy the root path, 
+        // producing a new tree of nodes that also have OwnerId.None.
+        var newRoot = BTreeFunctions.Set(_root, key, value, _strategy, OwnerId.None, out bool countChanged);
+        return new PersistentOrderedMap<K, V, TStrategy>(newRoot, _strategy, countChanged ? Count + 1 : Count);
+    }
+   
+    public static PersistentOrderedMap<K, V, TStrategy> Empty(TStrategy strategy)
+    {
+        // Create an empty Leaf Node.
+        // 'default(OwnerId)' (usually 0) marks this node as Immutable/Persistent.
+        // This ensures that any subsequent Set/Remove will clone this node 
+        // instead of modifying it in place.
+        var emptyRoot = new LeafNode<K, V>(default(OwnerId), strategy.UsesPrefixes);
+    
+        return new PersistentOrderedMap<K, V, TStrategy>(emptyRoot, strategy, 0);
+    }
+
+    public PersistentOrderedMap<K, V, TStrategy> Remove(K key)
+    {
+        var newRoot = BTreeFunctions.Remove<K,V, TStrategy>(_root, key, _strategy, OwnerId.None, out bool removed);
+        if (!removed) return this;
+        return new PersistentOrderedMap<K, V, TStrategy>(newRoot, _strategy, Count - 1);
+    }
+
+    public TransientOrderedMap<K, V, TStrategy> ToTransient()
+    {
+        return new TransientOrderedMap<K, V, TStrategy>(_root, _strategy, Count);
+    }
+}