SC-4Tasks
Share cards per piece
A piece with no image of its own still unfurls as the site wordmark.
/opengraph-image generates the Orbitron card for the whole site. A piece
with an image in its frontmatter already overrides it.
The gap is pieces without one: a [slug]/opengraph-image.tsx could render
the title onto the card so a shared link shows what it actually is.