fix(toptab): size each tab selectable to its label width

HellionChat/Ui/Components/TopTabBar.cs

@@ -25,12 +25,17 @@ internal sealed class TopTabBar
                 ImGui.SameLine();
 
             var selected = ReferenceEquals(tab, activeTab);
+            // Size the selectable to its own label width. A zero width makes ImGui
+            // stretch the selectable's box to the full remaining window width
+            // (imgui_widgets.cpp:7378), so in this SameLine row every tab overlaps
+            // into one giant bar and clicking never lands on the intended tab.
+            var tabWidth = ImGui.CalcTextSize(tab.Name).X;
             if (
                 ImGui.Selectable(
                     $"{tab.Name}###hellion_toptab_{i}",
                     selected,
                     ImGuiSelectableFlags.None,
-                    new Vector2(0, 0)
+                    new Vector2(tabWidth, 0)
                 )
             )
             {