fix(session): stop the session script's own loops when steam exits

tools/linuxfs/overlay/usr/local/bin/bannerlator-session

@@ -591,6 +591,10 @@ BUSCONF
         wait "$decky_supervisor" 2>/dev/null || true
         echo "== Decky: session supervisor stopped"
       fi
+      # This script's own loops and daemons (the fill-screen watcher never ends) would pass to
+      # gamescope's reaper when it exits and hold the compositor up on a black screen.
+      _bl_jobs=$(jobs -p)
+      [ -n "$_bl_jobs" ] && kill $_bl_jobs 2>/dev/null
       reap_orphans
     fi
     exit "$rc"