feat: astro built-ins — news pagination, prefetch, RSS, OG/SEO meta, TOC scrollspy (Starlight-pattern)

DESIGN.md

@@ -78,7 +78,8 @@ ctao.org animates nebula videos under Galaxy vignettes; our translation:
    already is its ambient; news/article/utility pages stay calm (reading
    focus). Body text NEVER sits on a moving gradient — cards, panels and
    bands are solid layers above it.
-3. One-shot hero `rise` stagger; hover lift/transitions. Nothing else.
+3. One-shot hero `rise` stagger; hover lift/transitions, incl. the card-cover
+   micro-zoom (scale 1.03, clipped by the card — AstroWind pattern). Nothing else.
 
 Rules:
 - ALL `animation`/`transition` declarations live inside the single
@@ -114,6 +115,14 @@ displayed): `<details class="toc toc--inline">` collapsed under the title
 (< 1200px) and `<nav class="toc toc--rail">` sticky right rail (≥ 1200px,
 outside the 70ch column via `.article-layout` grid). MDN/Stripe/NN-g pattern.
 
+Scrollspy (Starlight's starlight-toc pattern, minimal vanilla): an
+IntersectionObserver band under the sticky header maps the visible prose block
+to its governing heading and sets `aria-current="true"` on the TOC link
+(Galaxy + 600 weight). Functional state, not motion — the "no JS motion" rule
+is untouched; the TOC works fully without JS. Same precedent covers the search
+`<mark>` term highlight (Cherenkov tint) and the `.pagination` pill nav
+(Galaxy pill = current page, 44px targets).
+
 ## Do not
 
 - No new hues, tints, or grays — derive via `color-mix` from brand tokens only.