Replaces the legacy Zola script, which was hard-coded to the retired
"CASE FILE" branding, with scripts/generate-og-images.astro-site.mjs
built on the new design system's dark palette + Fraunces/JetBrains Mono.
Base.astro now renders og:image/twitter:image from a per-page ogImage
prop, wired into the writings and bookshelf detail pages.
Uses static-weight Fraunces/Newsreader font packages rather than the
variable fonts the site ships elsewhere, since satori's opentype.js
parser throws on their fvar table.
