Fix TreeControl highlight width when node text contains Spectre markup

Change measurement cache from StripAnsiStringLength to StripSpectreLength
so markup tags like [yellow] are excluded from visible width calculation.
Escape expand indicators [-]/[+] as [[-]]/[[+]] so they coexist with
Spectre markup in node text without causing parse failures.

Author: nickprotop

SharpConsoleUI/Controls/TreeControl/TreeControl.Rendering.cs

@@ -101,7 +101,7 @@ public override LayoutSize MeasureDOM(LayoutConstraints constraints)
 				bool[] ancestorIsLast = GetAncestorIsLastArray(node);
 				string prefix = BuildTreePrefix(depth, ancestorIsLast, guideChars);
 				string displayText = node.Text ?? string.Empty;
-				string expandIndicator = node.Children.Count > 0 ? "[-] " : "";
+				string expandIndicator = node.Children.Count > 0 ? "[[-]] " : "";
 				int itemWidth = GetCachedTextLength(prefix + expandIndicator + displayText);
 				if (itemWidth > maxItemWidth) maxItemWidth = itemWidth;
 			}
@@ -238,7 +238,8 @@ public override void PaintDOM(CharacterBuffer buffer, LayoutRect bounds, LayoutR
 				}
 
 				// Add expand/collapse indicator on the left side
-				string expandIndicator = node.Children.Count > 0 ? (node.IsExpanded ? "[-] " : "[+] ") : "";
+				// Escape brackets so Spectre markup in displayText (e.g. colored badges) is processed correctly
+				string expandIndicator = node.Children.Count > 0 ? (node.IsExpanded ? "[[-]] " : "[[+]] ") : "";
 
 				// Build full node text
 				string nodeText = prefix + expandIndicator + displayText;

SharpConsoleUI/Controls/TreeControl/TreeControl.cs

@@ -47,7 +47,7 @@ public partial class TreeControl : BaseControl, IInteractiveControl, IFocusableC
 		private int _lastClickIndex = -1;
 
 		// Performance: Cache for expensive text measurement operations
-		private readonly TextMeasurementCache _textMeasurementCache = new(AnsiConsoleHelper.StripAnsiStringLength);
+		private readonly TextMeasurementCache _textMeasurementCache = new(AnsiConsoleHelper.StripSpectreLength);
 
 		// Read-only helpers
 		private int CurrentSelectedIndex => _selectedIndex;
@@ -83,7 +83,7 @@ public override int? ContentWidth
 					bool[] ancestorIsLast = GetAncestorIsLastArray(node);
 					string prefix = BuildTreePrefix(depth, ancestorIsLast, guideChars);
 					string displayText = node.Text ?? string.Empty;
-					string expandIndicator = node.Children.Count > 0 ? " [-]" : "";
+					string expandIndicator = node.Children.Count > 0 ? " [[-]]" : "";
 					int length = GetCachedTextLength(prefix + displayText + expandIndicator);
 					if (length > maxLength) maxLength = length;
 				}