Commit 1709cb7 deleted the pinned hello-world post and ten tests
silently rotted with it - invisible until now because the suite could
not run in this clone (incomplete deps, then the broken frontmatter).
The slug, banner, og-meta and tag tests now derive slug and title from
the compiled posts at runtime (newest live post, newest draft), matching
the existing latest_post_with_links pattern, so content churn no longer
breaks them.