A link to the site shares as a card

Every page now carries the Open Graph and Twitter metadata a shared link needs: the page's own title and description, and one share image with the mark and the tagline. Paste a docs page into Discord, Slack or a post and it renders as a card instead of a bare URL. The .txt surfaces (llms.txt, robots.txt) also declare UTF-8 now; a reader without a charset was showing an ellipsis as three symbols.