Timer in UserActivity, change semantics to "user probably looks at app"
Before, UserActivitity emitting actions meant that the user had very recently interaction with their hardware.
Now it means they are likely looking at the app.
You can attach a timer that is aborted when we think the user
stops looking at the page
(or hasn't touched their hardware for 2 minutes).
This works better than the previous approach for larger timeouts,
like the 30s we're about to implement for out-of-view RMs