Allow smaller minimum width when in focus mode

It is not current possible to resize the terminal window so that is narrower than around 460px. I'm guessing this is to ensure there is enough room for tab headers and title bar etc. However, it would be desirable, when in focus mode, to be able to narrow the window further. This would facilitate simple "kiosk" apps (like the old Windows "widgets"). E.g. in the picture below, output is from a periodic script and is guaranteed never to exceed the text width being shown. I'd like to be able to make the terminal window narrower to fit the text to avoid wasting screen real-estate.

Note this is not the same as #6820 although it is related. That request is to prevent the user from narrowing the window beyond a certain threshold.