feat: The shortcut's window closes itself after a countdown

- 10-second countdown after the wizard ends (Enter closes right away); after an error it waits for Enter.
- pipefail, so a failed download counts as an error.

lib/wizard-shortcut.sh

@@ -37,12 +37,22 @@ launcher_enable() {
     install_executable "$WIZARD_LAUNCHER" 755 << EOF
 #!/bin/bash
 # Installed by Steamify CachyOS: run its newest release.
+# pipefail: a failed download must count as a failure, not an empty script.
+set -o pipefail
 if ! curl -fsSL --max-time 30 "$WIZARD_URL" | bash; then
     echo
     echo "Couldn't download or run the wizard. Are you connected to the internet?"
+    echo
+    read -rp "Press Enter to close this window... " _
+    exit 1
 fi
+# Done: close the window after a countdown (Enter closes it right away).
+echo
+for (( i = 10; i > 0; i-- )); do
+    printf '\rClosing this window in %2d seconds (Enter to close now)... ' "\$i"
+    read -rs -t 1 _ && break
+done
 echo
-read -rp "Press Enter to close this window... " _
 EOF
 
     # The icon comes with the release; without it, Steam's own icon.