fix(landing): use blog metadata for social previews

[siisee11]

One-Line Summary

Blog links shared to Slack now show the individual post title and thumbnail instead of falling back to generic OneQuery metadata.

User-Facing Changes

• Slack and other social unfurls show the blog post title without the site-title suffix.
• Every blog cover image, including square thumbnails, is used for the social preview.

Why This Changed

The previous selector accepted only wide images with a 1.45–2.2 aspect ratio and at least 1200px width. The Jam post uses a 1254×1254 cover, so it was rejected and the page fell back to the generic OneQuery image. Open Graph title also inherited the document title suffix.

How It Changed

• Source Open Graph and Twitter images directly from each post’s coverImage.
• Add an explicit ogTitle metadata property while retaining the SEO document title.
• Add a regression test for a square blog thumbnail.

Bug Fixes

• Square-cover blog posts no longer fall back to the generic OneQuery social image.
• Blog Open Graph titles now use the post title.

Verification

• bun run format
• bun run typecheck
• MISE_AUTO_INSTALL=0 mise exec -- bun run build
• MISE_AUTO_INSTALL=0 mise exec -- bunx turbo test --json (20/20 tasks passed)
• bun run --cwd apps/landing test (28/28 tests passed)
• Changed-file Oxlint and Oxfmt checks
• Rendered the Jam post locally and verified og:title, og:image, Twitter title/image, and 1254×1254 dimensions
• bun run knip could not complete because the local ignored .onequery/dev/secrets.toml profile is missing required sections

Video / Screenshot (Optional)

N/A