Revert "Hide the split button when the panel has only one tab"

This reverts commit e83ac75.

Author: charlesvien

apps/twig/src/renderer/features/panels/components/TabbedPanel.tsx

@@ -202,7 +202,7 @@ export const TabbedPanel: React.FC<TabbedPanelProps> = ({
                 background: "var(--color-background)",
               }}
             >
-              {onSplitPanel && content.tabs.length > 1 && (
+              {onSplitPanel && (
                 <TabBarButton
                   ariaLabel="Split panel"
                   onClick={handleSplitClick}