v0.4.2 — clean uninstall + Steam-closed install

Refinements to the install lifecycle from v0.4.1.

Changes

• --remove is now a full clean uninstall: it restores the vanilla game and deletes the <game-dir>.vanilla backup (no leftover restore point). --reinstall still keeps/rebuilds that backup.
• Steam install requires Steam closed: install / reinstall / --remove now abort up front if Steam is running, instead of doing a partial install and asking you to re-run with --steam-config-only. Pass --no-steam-config to install without touching Steam's config (and run with Steam open).
• Pilots + user configs are still preserved across --reinstall (from v0.4.1).

Get it (no git needed)

curl -fL https://github.com/psoetens/xwau-linux/archive/refs/tags/v0.4.2.tar.gz | tar xz
cd xwau-linux-0.4.2

Prebuilt Windows binaries unchanged from v0.3.0/v0.4.1 (carried forward so this tag is self-contained).