Function whenInView

docs/src/javascripts/lifecycle.js:65–83

(el, fn)

  // ── Lazy: only fire when the element scrolls into view ──────────────────
  function whenInView(el, fn) {
    if (!el) return;
    if (REDUCED) {
      fn();
      return;
    }
    const obs = new IntersectionObserver(
      (entries) => {
        entries.forEach((e) => {
          if (e.isIntersecting) {
            obs.disconnect();
            fn();
          }
        });
      },
      { rootMargin: "0px 0px -10% 0px" }
    );
    obs.observe(el);
  }

  // Helper: build an SVG element from a string template.
  function svgEl(tag, attrs) {