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

components/layout/Header.tsx

@@ -1,19 +1,41 @@
+'use client';
+
+import { useState } from 'react';
+import { useScroll, useMotionValueEvent } from 'framer-motion';
 import { Wordmark } from '@/components/primitives/Wordmark';
 import { CTA } from '@/components/primitives/CTA';
 import { Container } from '@/components/primitives/Container';
+import { ProgresoLectura } from '@/components/primitives/ProgresoLectura';
 import { header } from '@/lib/content';
 
+// The header tightens once the reader leaves the hero: less chrome, more page.
+// Client component because the compaction needs scroll state on the <header>
+// itself; there is no server-rendered data here to lose.
 export function Header() {
+  const [compacto, setCompacto] = useState(false);
+  const { scrollY } = useScroll();
+
+  useMotionValueEvent(scrollY, 'change', (y) => {
+    // Hysteresis: compact past 120px, expand back below 60px, so a header
+    // sitting exactly on the threshold doesn't flicker.
+    setCompacto((actual) => (actual ? y > 60 : y > 120));
+  });
+
   return (
-    <header className="sticky top-0 z-50 border-b border-azul-profundo/10 bg-white/80 backdrop-blur">
-      <Container className="flex items-center justify-between py-3">
-        <a href="#top" aria-label="creeer — inicio">
-          <Wordmark size="md" />
+    <header
+      className={`sticky top-0 z-50 relative border-b border-azul-profundo/10 bg-white/80 backdrop-blur transition-[padding] duration-300 motion-reduce:transition-none ${
+        compacto ? 'py-0' : 'py-3'
+      }`}
+    >
+      <Container className="flex items-center justify-between">
+        <a href="#top" aria-label="creeer — inicio" className="block transition-transform duration-300 origin-left motion-reduce:transition-none">
+          <Wordmark size={compacto ? 'sm' : 'md'} />
         </a>
         <nav aria-label="Principal">
           <CTA href="#contacto" label={header.cta} variant="light" />
         </nav>
       </Container>
+      <ProgresoLectura />
     </header>
   );
 }

components/layout/__tests__/Header.test.tsx

@@ -14,4 +14,15 @@ describe('<Header />', () => {
     const cta = screen.getByRole('link', { name: /Hablemos/i });
     expect(cta).toHaveAttribute('href', '#contacto');
   });
+  it('shows reading progress', () => {
+    const { container } = render(<Header />);
+    expect(container.querySelector('.bg-dorado')).toBeInTheDocument();
+  });
+
+  it('starts roomy, before any scrolling has happened', () => {
+    const { container } = render(<Header />);
+    // The header compacts on scroll; at rest it must be in its tall state, or
+    // the wordmark would land already shrunken on first paint.
+    expect(container.querySelector('header')?.className).toContain('py-3');
+  });
 });

components/primitives/ProgresoLectura.tsx

@@ -0,0 +1,24 @@
+'use client';
+
+import { motion, useScroll, useSpring } from 'framer-motion';
+import { usePrefersReducedMotion } from '@/lib/motion';
+
+// Reading progress along the bottom edge of the header. Pure motion feedback:
+// under reduced motion it renders nothing at all, because a static progress
+// bar communicates nothing — unlike an illustration, there is no meaningful
+// still frame of it.
+export function ProgresoLectura({ className = '' }: { className?: string }) {
+  const reduced = usePrefersReducedMotion();
+  const { scrollYProgress } = useScroll();
+  const avance = useSpring(scrollYProgress, { stiffness: 120, damping: 30, restDelta: 0.001 });
+
+  if (reduced) return null;
+
+  return (
+    <motion.div
+      aria-hidden="true"
+      className={`absolute bottom-0 left-0 right-0 h-0.5 origin-left bg-dorado ${className}`}
+      style={{ scaleX: avance }}
+    />
+  );
+}

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');
+  });
+});