feat: 项目初始化 + 3D方块世界原型 + AI助搭系统

初始化 monorepo: Go后端(7微服务) + Unity客户端(9模块) + 启动器

HTML5原型: Three.js 3D体素世界, Perlin噪声地形, 原版材质, 22种方块

Minecraft创造模式背包: 双栏布局, 拖拽移动物品, 方向性元件引脚

AI助搭策划文档 + 客户端/服务端骨架 + Docker Compose + CI

launcher/PCL-CE/PCL.Core/Utils/StringStream.cs

@@ -0,0 +1,49 @@
+using System;
+using System.IO;
+using System.Text;
+
+namespace PCL.Core.Utils;
+
+public class StringStream : Stream
+{
+    private readonly MemoryStream _innerStream;
+
+    /// <summary>
+    /// 使用指定编码初始化 StringStream。
+    /// </summary>
+    public StringStream(string source, Encoding? encoding = null)
+    {
+        ArgumentNullException.ThrowIfNull(source);
+        encoding ??= Encoding.UTF8;
+
+        var buffer = encoding.GetBytes(source);
+        _innerStream = new MemoryStream(buffer);
+    }
+
+    public override bool CanRead  => _innerStream.CanRead;
+    public override bool CanSeek  => _innerStream.CanSeek;
+    public override bool CanWrite => false;
+    public override long Length   => _innerStream.Length;
+
+    public override long Position
+    {
+        get => _innerStream.Position;
+        set => _innerStream.Position = value;
+    }
+
+    public override void Flush() { /* 只读流 无需实现 */ }
+
+    public override int Read(byte[] buffer, int offset, int count) => _innerStream.Read(buffer, offset, count);
+
+    public override long Seek(long offset, SeekOrigin origin) => _innerStream.Seek(offset, origin);
+
+    public override void SetLength(long value) => throw new NotSupportedException("StringStream 是只读流，不支持 SetLength。");
+
+    public override void Write(byte[] buffer, int offset, int count) => throw new NotSupportedException("StringStream 是只读流，不支持 Write。");
+
+    protected override void Dispose(bool disposing)
+    {
+        if (disposing) _innerStream.Dispose();
+        base.Dispose(disposing);
+    }
+}