monitor inactive or idol task status, poll for info (#166)

* wip #254671

* get it working

* register disposables

* improve comment

* good state

* get it to work

* rm comment

* improvements

* update baseline

* only include tasks for which there's a terminal

* fix bug

* improve

* fix tests

* add inactive task test

* don't leak listener

* System -> User

* add semicolons

* fix issue

* add semicolon

* Also check for idle

* monitor inactive

* update engine

* cleanup

* add a comment

* consolidate

* fix tests