Union.Manifold v3.6.10

Fixed

• Auto-update manifest could drop platforms: every platform job uploaded
  its own latest.json and the uploads raced read-modify-write on the
  same release asset, so whichever job finished last decided which
  platforms the updater knew about. The manifest is now built once, after
  all builds finish, from the release's own signature files, and always
  covers Windows, Linux (AppImage, deb, RPM), and both macOS arches.