feat(header): progreso de lectura y compactado al bajar

components/primitives/__tests__/ProgresoLectura.test.tsx

@@ -0,0 +1,17 @@
+import { render } from '@testing-library/react';
+import { describe, it, expect } from 'vitest';
+import { ProgresoLectura } from '../ProgresoLectura';
+
+describe('<ProgresoLectura />', () => {
+  it('is decorative: hidden from assistive tech', () => {
+    const { container } = render(<ProgresoLectura />);
+    expect(container.firstElementChild).toHaveAttribute('aria-hidden', 'true');
+  });
+
+  it('renders as a gold rule anchored to the bottom edge', () => {
+    const { container } = render(<ProgresoLectura />);
+    const cls = container.firstElementChild?.className ?? '';
+    expect(cls).toContain('bg-dorado');
+    expect(cls).toContain('absolute');
+  });
+});