Uses IntersectionObserver on each section element. Multiple thresholds
(0, 0.1, 0.25, 0.5, 0.75, 1.0) track the intersection ratio of every
section simultaneously; whichever has the highest visible ratio at any
moment becomes the active item. rootMargin offsets for the sticky nav
height so a section is only considered active once it's genuinely in
view beneath the bar.
Active link gets .sectionNavLinkActive — coral background + white text,
matching the phase tab active style used elsewhere in the product.
Observer is cleaned up on unmount.
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
Tudor Sitaru
536a166b35