fix third core dump on export option

hanatui/src/Tui/Components/StatsPanel.cs

@@ -98,6 +98,7 @@ public static class StatsPanel
     /// <summary>
     /// Renders a horizontal block bar of the given width.
     /// e.g.  [████████░░░░]
+    /// Result is a markup string safe for embedding inside a larger Markup call.
     /// </summary>
     private static string BuildBar(double percent, int width, string color)
     {
@@ -105,8 +106,11 @@ public static class StatsPanel
         filled = Math.Clamp(filled, 0, width);
         var empty = width - filled;
 
-        var bar = new string('\u2588', filled) + new string('\u2591', empty);
-        return $"[[{color}]{bar}[/]]";
+        // \u2588 = █  \u2591 = ░
+        // [[ and ]] are Spectre escape sequences for literal [ and ]
+        var filledStr = new string('\u2588', filled);
+        var emptyStr  = new string('\u2591', empty);
+        return $"[[[{color}]{filledStr}[/][dim]{emptyStr}[/]]]";
     }
 
     private static string CpuColor(double pct) => pct switch