Umbra Studio v0.22.0

BAT-First Windows Release

• Replaced the Windows EXE release with a BAT-only portable package that starts
  Umbra through the bundled Bun runtime.
• Removed the native Windows launcher compiler and executable from the source,
  package builder, release workflow, and release archive.
• Changed the Windows release asset to
  Umbra-Studio-v0.22.0-Windows-x64-BAT.zip so legacy EXE updaters cannot
  mistake the launcher transition for an in-place compatible update.
• Made BAT the preferred launcher when an older executable is also present,
  while retaining EXE detection solely for migration from older portable builds.
• Existing EXE installations require a one-time manual migration: extract the
  v0.22.0 BAT package and move the previous User and Tools folders into its
  Umbra Studio folder. Future BAT releases can then use Umbra Updater normally.