Expose ITerminal.Width property

src/System.CommandLine.Rendering/ITerminal.cs

@@ -22,5 +22,7 @@ public interface ITerminal : IConsole
         void HideCursor();
 
         void ShowCursor();
+
+        int Width { get; }
     }
 }

src/System.CommandLine.Rendering/SystemConsoleTerminal.cs

@@ -1,6 +1,8 @@
 // Copyright (c) .NET Foundation and contributors. All rights reserved.
 // Licensed under the MIT license. See LICENSE file in the project root for full license information.
 
+using System.CommandLine.IO;
+
 namespace System.CommandLine.Rendering
 {
     public class SystemConsoleTerminal : TerminalBase
@@ -22,6 +24,8 @@ public override ConsoleColor BackgroundColor
             set => System.Console.BackgroundColor = value;
         }
 
+        public override int Width => Console is SystemConsole system ? system.GetConsoleWindowWidth() : int.MaxValue;
+
         public override ConsoleColor ForegroundColor
         {
             get => System.Console.ForegroundColor;

src/System.CommandLine.Rendering/TerminalBase.cs

@@ -45,6 +45,8 @@ protected TerminalBase(IConsole console)
 
         public bool IsInputRedirected => Console.IsInputRedirected;
 
+        public abstract int Width { get; }
+
         protected virtual void Dispose(bool disposing)
         {
         }

src/System.CommandLine.Rendering/TestTerminal.cs

@@ -70,7 +70,7 @@ private void OnCharWrittenToOut(char c)
 
         public int Height { get; set; } = 100;
 
-        public int Width { get; set; } = 100;
+        public int Width { get; } = 100;
 
         public virtual void ResetColor()
         {

src/System.CommandLine.Rendering/VirtualTerminal.cs

@@ -26,6 +26,8 @@ public override void ResetColor()
                 Ansi.Color.Foreground.Default.EscapeSequence);
         }
 
+        public override int Width => int.MaxValue;
+
         public override void Clear()
         {
             Console.Out.Write(