refactor: best_effort log for quiet steps, registered temp dirs, one exit handler

Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01Ss5gKj7XG5JPi27XwGBGTs

lib/state.sh

@@ -123,7 +123,7 @@ migrate_layout() {
             "$(wizard_desktop_dir)/$WIZARD_DESKTOP_NAME"; do
             [[ -f "$f" ]] && sed -i "s|$old_bin/|$STEAMIFY_BIN/|g" "$f"
         done
-        user_systemctl daemon-reload 2>/dev/null
+        best_effort user_systemctl daemon-reload
     fi
     if [[ -f "$old_icon" ]]; then
         if [[ -e "$WIZARD_ICON" ]]; then rm -f "$old_icon"; else mv "$old_icon" "$WIZARD_ICON"; fi