If you're sitting in the office waiting for something to build, and you get out your phone to go on HN I'm sorry to say that is probably not the sort of professionalism that's going to afford you much protection from layoffs.
Been in the industry for a while now, no one cares if you pull out your phone. Generally, people treat others like adults not children.
It was a public case, but the essentially unanimous Supreme Court opinion in City of Ontario v. Quon [0, 2010] shows what expectations of privacy you should have on any work devices -- none.
Reasonable or limited private use of a work computer remains private.
https://edps.europa.eu/data-protection/data-protection/refer...