feat: add scroll functionality for height-limited panels

Adds a new Scroll property to Panel widget that controls content behavior when exceeding height:
- When true: shows most recent content (scrolling)
- When false: truncates excess content (default behavior)

Author: rocklau

src/Spectre.Console/Widgets/Panel.cs

@@ -45,6 +45,12 @@ public sealed class Panel : Renderable, IHasBoxBorder, IHasBorder, IExpandable,
     /// </summary>
     public int? Height { get; set; }
 
+    /// <summary>
+    /// Gets or sets a value indicating whether content should scroll when exceeding height.
+    /// If true, shows most recent content; if false, truncates excess content.
+    /// </summary>
+    public bool Scroll { get; set; }
+
     /// <summary>
     /// Gets or sets a value indicating whether or not the panel is inlined.
     /// </summary>
@@ -144,7 +150,15 @@ protected override IEnumerable<Segment> Render(RenderOptions options, int maxWid
 
         // Split the child segments into lines.
         var childSegments = ((IRenderable)child).Render(options with { Height = height }, innerWidth);
-        foreach (var (_, _, last, line) in Segment.SplitLines(childSegments, innerWidth, height).Enumerate())
+        var allLines = Segment.SplitLines(childSegments, innerWidth, null).ToList();
+
+        // If scrolling is enabled and content exceeds height limit, keep only the last few lines
+        if (Scroll && height.HasValue && allLines.Count > height.Value)
+        {
+            allLines = allLines.Skip(allLines.Count - height.Value).ToList();
+        }
+
+        foreach (var (_, _, last, line) in allLines.Enumerate())
         {
             if (line.Count == 1 && line[0].IsWhiteSpace)
             {
@@ -231,4 +245,4 @@ private void AddTopBorder(
         result.Add(new Segment(border.GetPart(BoxBorderPart.TopRight), borderStyle));
         result.Add(Segment.LineBreak);
     }
-}
+}