Enable property-level string interning via attribute

Introduce [AcStringIntern] for selective string interning on properties. Update serializer to use a per-property eligibility flag, improving efficiency and control over which string fields participate in interning during binary serialization. Update test models and internal context accordingly.

AyCode.Core.Tests/TestModels/AcSerializerModels.cs

@@ -1,4 +1,5 @@
 using AyCode.Core.Interfaces;
+using AyCode.Core.Serializers.Binaries;
 
 namespace AyCode.Core.Tests.TestModels;
 
@@ -30,7 +31,9 @@ public static class AcSerializerModels
 
     public class TestClassWithRepeatedStrings
     {
+        [AcStringIntern(true)]
         public string Field1 { get; set; } = "";
+        [AcStringIntern(true)]
         public string Field2 { get; set; } = "";
         public string Field3 { get; set; } = "";
         public string Field4 { get; set; } = "";

AyCode.Core.Tests/TestModels/SharedTestModels.cs

@@ -1,6 +1,7 @@
 using AyCode.Core.Extensions;
 using AyCode.Core.Interfaces;
 using AyCode.Core.Serializers.Attributes;
+using AyCode.Core.Serializers.Binaries;
 using AyCode.Core.Serializers.Jsons;
 using MessagePack;
 using MongoDB.Bson.Serialization.Attributes;
@@ -60,6 +61,7 @@ public class SharedTag : IId<int>
     public int Id { get; set; }
     [Key(1)]
     public string Name { get; set; } = "";
+    [AcStringIntern(true)]
     [Key(2)]
     public string Color { get; set; } = "#000000";
     [Key(3)]
@@ -133,12 +135,15 @@ public class SharedUser : IId<int>
 [MessagePackObject]
 public class UserPreferences
 {
+    [AcStringIntern(true)]
     [Key(0)]
     public string Theme { get; set; } = "light";
+    [AcStringIntern(true)]
     [Key(1)]
     public string Language { get; set; } = "en-US";
     [Key(2)]
     public bool NotificationsEnabled { get; set; } = true;
+    [AcStringIntern(true)]
     [Key(3)]
     public string? EmailDigestFrequency { get; set; }
 }
@@ -155,8 +160,10 @@ public class UserPreferences
 [MessagePackObject]
 public class MetadataInfo
 {
+    [AcStringIntern(true)]
     [Key(0)]
     public string Key { get; set; } = "";
+    [AcStringIntern(true)]
     [Key(1)]
     public string Value { get; set; } = "";
     [Key(2)]
@@ -240,6 +247,7 @@ public class TestOrderItem : IId<int>
 {
     [Key(0)]
     public int Id { get; set; }
+    [AcStringIntern(true)]
     [Key(1)]
     public string ProductName { get; set; } = "";
     [Key(2)]

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

@@ -146,6 +146,13 @@ public static partial class AcBinarySerializer
         /// <summary>Write pass visit counter. Mirrors ScanVisitIndex ordering.</summary>
         internal int WriteVisitIndex;
 
+        /// <summary>
+        /// Set per-property in WritePropertyOrSkip before calling WriteString.
+        /// Controls whether the current string property participates in the cursor-based interning.
+        /// Must mirror scan pass's prop.UseStringPropertyInterning() check.
+        /// </summary>
+        internal bool StringInternEligible;
+
         /// <summary>
         /// Tries to consume the next write plan entry at the current WriteVisitIndex.
         /// Returns true if the entry matches (duplicate exists at this visit point).
@@ -264,6 +271,7 @@ public static partial class AcBinarySerializer
             ScanVisitIndex = 0;
             WritePlanCursor = 0;
             WriteVisitIndex = 0;
+            StringInternEligible = false;
 
             // Clear write plan string references to avoid GC pinning, keep array if small enough
             if (_writePlan != null)

AyCode.Core/Serializers/Binaries/AcBinarySerializer.cs

@@ -912,8 +912,10 @@ public static partial class AcBinarySerializer
             return;
         }
 
-        if (context.UseStringInterning && context.IsValidForInterningString(value.Length))
+        if (context.StringInternEligible && context.IsValidForInterningString(value.Length))
         {
+            context.StringInternEligible = false;
+
             if (context.TryConsumeWritePlanEntry(out var planEntry))
             {
                 ValidateWritePlanString(in planEntry, value);
@@ -1383,6 +1385,7 @@ public static partial class AcBinarySerializer
                     }
                     else
                     {
+                        context.StringInternEligible = prop.UseStringPropertyInterning(context.Options.UseStringInterning);
                         WriteString(value, context);
                     }
                     return;
@@ -1391,6 +1394,8 @@ public static partial class AcBinarySerializer
                 {
                     // Object type (collection, complex object, byte[], dictionary)
                     // Use pre-cached wrapper, fallback to GetWrapper on miss/polymorphism
+                    // Set interning eligibility for string collection elements
+                    context.StringInternEligible = prop.IsStringCollectionProperty && prop.UseStringPropertyInterning(context.Options.UseStringInterning);
                     var value = prop.GetValue(obj);
 
                     // SKIP marker only for null (reference types)
@@ -1736,10 +1741,7 @@ public static partial class AcBinarySerializer
     /// Uses the typed Id getter to extract the Id and compares against the scan pass IdentityMap.
     /// </summary>
     [Conditional("DEBUG")]
-    private static void ValidateWritePlanObject(
+    private static void ValidateWritePlanObject(in WriteDuplicateEntry planEntry, object value, TypeMetadataWrapper<BinarySerializeTypeMetadata> wrapper)
-        in WriteDuplicateEntry planEntry,
-        object value,
-        TypeMetadataWrapper<BinarySerializeTypeMetadata> wrapper)
     {
         var metadata = wrapper.Metadata;
         switch (metadata.IdAccessorType)