v0.13.1

Changed

• npm and MCP Registry listing metadata: bugs URL, core keywords, and
  server.json title/repository/websiteUrl.
• release.sh writes a ## [x.y.z] changelog entry for every release --
  promoting [Unreleased] when it has content, otherwise generating one from
  the commit subjects since the previous tag -- keeps Keep-a-Changelog link
  references current when a file has them, and takes the GitHub release notes
  from that entry instead of from git log subjects. Before this, a release
  with nothing under [Unreleased] got no entry at all, and every GitHub
  release page showed raw commit subjects.