feat(renderer): TabBar skeleton (no tabs yet — wired in Phase 5)

src/renderer/components/layout/TabBar.tsx

@@ -0,0 +1,7 @@
+export function TabBar() {
+  return (
+    <div className="flex h-9 items-center border-b border-border bg-card/20 px-3 text-xs text-muted-foreground">
+      <span>No files open</span>
+    </div>
+  );
+}

tests/component/layout/TabBar.test.tsx

@@ -0,0 +1,10 @@
+import { describe, it, expect } from 'vitest';
+import { render, screen } from '@testing-library/react';
+import { TabBar } from '@/components/layout/TabBar';
+
+describe('TabBar', () => {
+  it('renders an empty state when no tabs are open', () => {
+    render(<TabBar />);
+    expect(screen.getByText(/no files open/i)).toBeInTheDocument();
+  });
+});