A shared /watch/{token} link is a client-rendered SPA, so a social crawler only
saw the generic index.html — a blank link card. The server now injects per-video
Open Graph / Twitter tags (title, channel, thumbnail) into the served HTML for
that route, so links unfurl richly in Messenger and other chat apps; real
browsers ignore the extra tags and hydrate the page as usual. Password /
expired / invalid links fall back to the generic card with no metadata leak.
Also shortens the generic site description used for search engines and link
previews.
