Update string serialization to always write length prefix

- Always write length prefix before ASCII and UTF-8 strings in AcBinarySerializer for consistency and correctness.
- Increase release warmup iterations from 2000 to 3000 in Program.cs.

AyCode.Core.Serializers.Console/Program.cs

@@ -49,7 +49,7 @@ public static class Program
     private static int WarmupIterations = 5;
     private static int TestIterations = 10;
     #else
-    private static int WarmupIterations = 2000;
+    private static int WarmupIterations = 3000;
     private static int TestIterations = 1000;
 
     //private static int WarmupIterations = 5000;

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

@@ -487,6 +487,7 @@ public static partial class AcBinarySerializer
             // Single-pass Ascii.FromUtf16 (scan+copy combined) instead of
             // Ascii.IsValid (scan) + Ascii.FromUtf16 (scan+copy) = double traversal
             var savedPosition = _position;
+
             WriteVarUInt((uint)charLength);
             EnsureCapacity(charLength);
 
@@ -500,8 +501,10 @@ public static partial class AcBinarySerializer
             // FromUtf16 fails fast on first non-ASCII char, so speculative cost is minimal
             _position = savedPosition;
             var byteCount = Utf8NoBom.GetByteCount(value);
+
             WriteVarUInt((uint)byteCount);
             EnsureCapacity(byteCount);
+
             Utf8NoBom.GetBytes(value.AsSpan(), _buffer.AsSpan(_position, byteCount));
             _position += byteCount;
         }