deck mode: jupiter-dock-updater --check answers 7 (up to date); exit 0 read as an update waiting and showed a Dock Firmware Update row

tools/linuxfs/overlay/usr/bin/steamos-polkit-helpers/jupiter-dock-updater

@@ -1,4 +1,9 @@
 #!/bin/sh
-# No Deck dock here. The client calls this from the polkit-helpers directory in Deck mode; a
-# clean exit is "nothing to update".
+# No Deck dock here. The client runs this with --check at start (systemdockmanager.txt) and reads
+# the exit code: 0 with nothing printed is taken as "an update is available" and puts a Dock
+# Firmware Update row with an Apply button in Settings > System. 7, SteamOS's "nothing to do",
+# is read as up to date (state 2 in that log, against state 4 for exit 0; both seen on device).
+case "${1:-}" in
+  --check) exit 7 ;;
+esac
 exit 0