feat(grafico): HiloConductor — la línea dorada que cose la página

components/primitives/HiloConductor.tsx

@@ -0,0 +1,72 @@
+'use client';
+
+import { motion, useScroll, useSpring } from 'framer-motion';
+import { usePrefersReducedMotion } from '@/lib/motion';
+
+// One continuous gold line running the height of the page, drawing itself as
+// the reader scrolls. It is the spine of the layout: it stitches the sections
+// together so the landing reads as a route rather than a stack of blocks.
+//
+// Positioned `absolute`, never `fixed` — the thread belongs to the document
+// and scrolls with it. A fixed layer would read as an ornament stuck to the
+// window.
+//
+// Uses the page-level useScroll() with no target ref on purpose: no element
+// measuring, no "container has a static position" warnings, and one scroll
+// listener for the whole page.
+
+const TRAZO =
+  'M50 0 C 20 140, 80 260, 50 400 C 20 540, 80 660, 50 800 C 20 940, 80 1060, 50 1200';
+
+export function HiloConductor({ className = '' }: { className?: string }) {
+  const reduced = usePrefersReducedMotion();
+  const { scrollYProgress } = useScroll();
+  const avance = useSpring(scrollYProgress, { stiffness: 90, damping: 30, restDelta: 0.001 });
+
+  const base = `pointer-events-none absolute inset-y-0 left-1/2 -translate-x-1/2 w-full max-w-content h-full ${className}`;
+
+  // The positioning/pointer-events classes live on a wrapping <div> rather
+  // than the <svg> itself: per spec `SVGElement.className` is an
+  // SVGAnimatedString, not a plain string, so tests (and any other reader of
+  // `.className`) can't inspect it as text. A plain HTMLElement keeps that
+  // contract simple.
+
+  // Plain <path> for reduced motion: motion.path applies dash scaffolding even
+  // without initial/animate and would leave the thread invisible.
+  if (reduced) {
+    return (
+      <div className={base}>
+        <svg
+          className="h-full w-full text-dorado/25"
+          viewBox="0 0 100 1200"
+          preserveAspectRatio="none"
+          aria-hidden="true"
+          focusable="false"
+        >
+          <path d={TRAZO} fill="none" stroke="currentColor" strokeWidth={1.5} strokeLinecap="round" />
+        </svg>
+      </div>
+    );
+  }
+
+  return (
+    <div className={base}>
+      <svg
+        className="h-full w-full text-dorado/25"
+        viewBox="0 0 100 1200"
+        preserveAspectRatio="none"
+        aria-hidden="true"
+        focusable="false"
+      >
+        <motion.path
+          d={TRAZO}
+          fill="none"
+          stroke="currentColor"
+          strokeWidth={1.5}
+          strokeLinecap="round"
+          style={{ pathLength: avance }}
+        />
+      </svg>
+    </div>
+  );
+}

components/primitives/__tests__/HiloConductor.test.tsx

@@ -0,0 +1,30 @@
+import { render } from '@testing-library/react';
+import { describe, it, expect } from 'vitest';
+import { HiloConductor } from '../HiloConductor';
+
+describe('<HiloConductor />', () => {
+  it('is decorative: hidden from assistive tech', () => {
+    const { container } = render(<HiloConductor />);
+    const svg = container.querySelector('svg');
+    expect(svg).toHaveAttribute('aria-hidden', 'true');
+    expect(svg).toHaveAttribute('focusable', 'false');
+  });
+
+  it('draws a single continuous thread', () => {
+    const { container } = render(<HiloConductor />);
+    expect(container.querySelectorAll('path')).toHaveLength(1);
+  });
+
+  it('travels with the document instead of sticking to the viewport', () => {
+    const { container } = render(<HiloConductor />);
+    // `fixed` would read as an ornament pinned to the window; the thread
+    // belongs to the page and must scroll with it.
+    expect(container.firstElementChild?.className).toContain('absolute');
+    expect(container.firstElementChild?.className).not.toContain('fixed');
+  });
+
+  it('stays out of the way of pointer input', () => {
+    const { container } = render(<HiloConductor />);
+    expect(container.firstElementChild?.className).toContain('pointer-events-none');
+  });
+});