feat: The script is now steamify.sh

- setup-gamescope-boot.sh renamed to steamify.sh; all references updated.
- Releases publish the bundle as steamify.sh and, for older install commands, setup-gamescope-boot.sh.
- The Steamify shortcut runs steamify.sh.

lib/steam-desktop.sh

@@ -1,7 +1,7 @@
 #!/bin/bash
 # Steam in the Plasma desktop session: gamepad UI args, virtual keyboard,
 # autostart. Part of the SteamOS conversion (gaming_enable/gaming_disable).
-# Sourced by setup-gamescope-boot.sh; not meant to be run on its own.
+# Sourced by steamify.sh; not meant to be run on its own.
 
 steam_enable() {
     info "Applying non-optional SteamOS environment & keyboard fixes..."