Phase 14 follow-up: Scoop / Windows packaging

[dekobon]

Track shipping a Scoop manifest (or Chocolatey package) for Windows
once the helper binaries support Windows builds.

Open questions to settle first:

• The current install workflow assumes POSIX symlinks for the +-form
  helper names. Windows alternatives (NTFS symlinks, hard links, copies)
  need a decision.
• The release workflow does not yet build *-pc-windows-msvc targets
  (.github/workflows/release.yml). That's a prerequisite.
• Locking semantics, LFS path layout, and stdout discipline need a CI
  pass on Windows before declaring support.

Tracked as a Phase 14 follow-up per #14.