Add ReferenceProperties for efficient reference tracking

Introduce a lazily-computed ReferenceProperties array to AcBinarySerializer, containing only complex and string properties. This enables efficient iteration and reference tracking during serialization by filtering relevant properties on first access.

AyCode.Core/Serializers/Binaries/AcBinarySerializer.BinarySerializeTypeMetadata.cs

@@ -55,6 +55,34 @@ public static partial class AcBinarySerializer
         /// </summary>
         private int[]? _metadataPropertyHashes;
 
+        /// <summary>
+        /// Lazy-computed array of reference properties (complex types + strings).
+        /// Used by scan pass to quickly iterate only properties that need reference tracking.
+        /// </summary>
+        private BinaryPropertyAccessor[]? _referenceProperties;
+
+        /// <summary>
+        /// Gets the array of reference properties (complex types + strings).
+        /// Computed lazily on first access.
+        /// </summary>
+        public BinaryPropertyAccessor[] ReferenceProperties
+        {
+            [MethodImpl(MethodImplOptions.AggressiveInlining)]
+            get => _referenceProperties ??= ComputeReferenceProperties();
+        }
+
+        [MethodImpl(MethodImplOptions.NoInlining)]
+        private BinaryPropertyAccessor[] ComputeReferenceProperties()
+        {
+            var list = new List<BinaryPropertyAccessor>();
+            foreach (var prop in Properties)
+            {
+                if (prop.IsComplexType || prop.AccessorType == PropertyAccessorType.String)
+                    list.Add(prop);
+            }
+            return list.ToArray();
+        }
+
         public int[] MetadataPropertyHashes
         {
             [MethodImpl(MethodImplOptions.AggressiveInlining)]