getActiveIds
Returns the ids of all Live Updates this app is currently showing.
Useful for reconciling app state with what is on screen — for example deciding whether to call endLiveUpdate for an activity the app already considers finished.
Safe to call from any thread; runs a short binder call to getActiveNotifications — keep it off the hot UI path.
Return
the activityIds of active Live Updates, or an empty list if none are shown (including on devices below API 36)