Fixed decoding of text "accumulating" over time (never properly clearing buffer)

LLama/LLamaStatelessExecutor.cs

@@ -100,7 +100,7 @@ namespace LLama
 
                 decoder.Add(id);
                 var decoded = decoder.Read();
-                yield return decoder.Read();
+                yield return decoded;
 
                 tokens.Clear();
                 tokens.Add(id);

LLama/Native/SafeLlamaModelHandle.cs

@@ -1,11 +1,7 @@
 using System;
-using System.Buffers;
 using System.Collections.Generic;
-using System.Diagnostics;
-using System.Runtime.InteropServices;
 using System.Text;
 using LLama.Exceptions;
-using LLama.Extensions;
 
 namespace LLama.Native
 {

LLama/StreamingTokenDecoder.cs

@@ -155,7 +155,12 @@ public sealed class StreamingTokenDecoder
     /// <returns></returns>
     public string Read()
     {
-        return string.Join("", _characters);
+        if (_characters.Count == 0)
+            return "";
+
+        var str = string.Join("", _characters);
+        _characters.Clear();
+        return str;
     }
 
     /// <summary>