v0.5.1

Fixed

• The browser suite passes on a project that has just taken 0.5.0. The
  section-page check drew its sample from the manifest and always expected the
  new listing, but section pages generated before 0.5.0 record no entries and,
  as intended, keep their Markdown list until the next sync rewrites them, so
  the upgrade's own pull request failed until a sync had run. The check now
  reads the sample page's frontmatter: a page without entries must show its
  Markdown list, linking the subfolder, and no listing.