Union.Manifold v3.6.8

Fixed

• Release pipeline: the 3.6.7 release shipped without its Windows
  installer, AppImage, deb, and macOS ARM builds. All four platform jobs
  raced to create the GitHub draft release, each created its own, and
  three of them (Windows included) stayed stranded as invisible drafts
  while only one got published. The draft release is now created once, up
  front, so every platform job uploads into the same release.