Root cause found: app.js sets opacity:0 + transform:translateY(16px) on
EVERY .card element at DOMContentLoaded, then relies on an
IntersectionObserver to reveal them. When cards are already in viewport
or content is tall, the observer fails to fire and cards stay invisible.

Zooming triggered a layout recalculation that forced the observer to
re-evaluate, making content reappear — explaining the user's symptom.
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>