feat(hilo): el conductor baja visible por el centro, tras el texto

components/primitives/__tests__/Container.test.tsx

@@ -0,0 +1,15 @@
+import { render } from '@testing-library/react';
+import { describe, it, expect } from 'vitest';
+import { Container } from '../Container';
+
+describe('<Container />', () => {
+  it('lifts its content above the conductor thread', () => {
+    const { container } = render(<Container>contenido</Container>);
+    const cls = container.firstElementChild?.className ?? '';
+    // The thread sits at z-10; the section backgrounds are z-auto. Lifting the
+    // content column to z-20 is what puts the text *above* a centred thread,
+    // so the spine reads behind the reading instead of across it.
+    expect(cls).toContain('relative');
+    expect(cls).toMatch(/\bz-20\b/);
+  });
+});