v0.4.2

Documentation only — no code change.

• Lead the WSL guidance with the polkit rule rather than running as root.
  Recommending root to library consumers pushes them to relay that to their
  own users, and most tools keep caches or configuration under $HOME, where
  running as root leaves artifacts the user can no longer modify. Keeping the
  client unprivileged is what PackageKit exists to make possible.
• Document that the suggested rule covers only install/remove/update.
  refreshCache maps to system-sources-refresh, which needs no
  authorization for a caller in a login session but does for one without —
  the CI and WSL case.