documentation update

Core/Collections/DataMap.cs

@@ -3,6 +3,11 @@ using System.Runtime.InteropServices;
 
 namespace Just.Core.Collections;
 
+/// <summary>
+/// A 2D grid with lazy min/max caching, cloning, and binary stream serialization.
+/// Requires <typeparamref name="T"/> to support comparison and equality operators.
+/// </summary>
+/// <typeparam name="T">The element type; must implement <c>IComparisonOperators&lt;T, T, bool&gt;</c> and <c>IEqualityOperators&lt;T, T, bool&gt;</c>.</typeparam>
 public class DataMap<T> : Map<T>, IDataMap<T>, ICloneable
     where T : IComparisonOperators<T, T, bool>, IEqualityOperators<T, T, bool>
 {