第 0 阶段：教材项目 2 任务 1 在网页中原样运行

- runtime：仿真 WinForms 子集（Form、Button、Label、TextBox、ComboBox、
  GroupBox、Timer、MessageBox、界面线程消息循环、跨线程检查）、
  教材设备类库（DeviceCtrlHelper、LED 控件）、运行器（常驻编译服务 + 运行模式）
- server：Bun + Hono，WebSocket 会话，每次运行一个进程，消息转发
- web：Vue + Naive UI，WinForms 风格窗体渲染、MessageBox、实训台 LED 屏
- 端到端测试与 100 个程序并发的压力测试
- 教材逐任务摘要（docs/教材摘要）

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

runtime/Sim.WinForms/Forms/MessageBox.cs

@@ -0,0 +1,45 @@
+using System.Text.Json.Nodes;
+using Sim.Host;
+
+namespace System.Windows.Forms;
+
+/// <summary>在浏览器里弹出对话框，阻塞到用户点击按钮后返回结果（期间界面线程照常处理 Timer 等消息）</summary>
+public static class MessageBox
+{
+    public static DialogResult Show(string? text) => Show(text, "");
+
+    public static DialogResult Show(string? text, string? caption) =>
+        Show(text, caption, MessageBoxButtons.OK, MessageBoxIcon.None);
+
+    public static DialogResult Show(string? text, string? caption, MessageBoxButtons buttons) =>
+        Show(text, caption, buttons, MessageBoxIcon.None);
+
+    public static DialogResult Show(string? text, string? caption, MessageBoxButtons buttons, MessageBoxIcon icon) =>
+        ShowCore(text, caption, buttons, icon);
+
+    public static DialogResult Show(string? text, string? caption, MessageBoxButtons buttons, MessageBoxIcon icon, MessageBoxDefaultButton defaultButton) =>
+        ShowCore(text, caption, buttons, icon);
+
+    public static DialogResult Show(IWin32Window? owner, string? text) => Show(text);
+
+    public static DialogResult Show(IWin32Window? owner, string? text, string? caption) => Show(text, caption);
+
+    public static DialogResult Show(IWin32Window? owner, string? text, string? caption, MessageBoxButtons buttons) =>
+        Show(text, caption, buttons);
+
+    public static DialogResult Show(IWin32Window? owner, string? text, string? caption, MessageBoxButtons buttons, MessageBoxIcon icon) =>
+        Show(text, caption, buttons, icon);
+
+    private static DialogResult ShowCore(string? text, string? caption, MessageBoxButtons buttons, MessageBoxIcon icon)
+    {
+        var reply = SimHost.Request(new JsonObject
+        {
+            ["type"] = "messageBox",
+            ["text"] = text ?? "",
+            ["caption"] = caption ?? "",
+            ["buttons"] = buttons.ToString(),
+            ["icon"] = icon.ToString(),
+        });
+        return Enum.TryParse<DialogResult>((string?)reply, out var result) ? result : DialogResult.Cancel;
+    }
+}