Pull request pages and /docs pages previously fell back to the generic site-level Open Graph card. Both now emit the same signed, content-versioned card images that repositories, issues, commits, and blobs already use. - The pull request card shows the title, author, `head → base` branches, a state chip (open, draft, merged, closed), and the stack position when the pull request belongs to a stack. - The docs card shows the section, page title, opening paragraph (links and code ticks flattened), the described route, and the heading count. - Docs cards render under `/og/v/:version/docs/:slug`; every repository resource stays under the `repos` scope, so existing card URLs are unchanged. - The image endpoint rebuilds pull request cards through the public-repository predicate, and docs cards only from the compile-time catalog, keeping the anonymous-data-only posture. Builds on #122 (the docs pages the docs cards describe), so it ships as layer 5 of the same stack.