New lines auto-scroll the view to the bottom; scrolling up to read now
pauses that (an amber 'paused' marker shows), and scrolling back to the
bottom resumes — the explicit Pause/Play button and the scroll position stay
in sync via a single at-bottom check. While paused, logs still stream in
below without moving the view. Jump-to-latest is instant rather than smooth
so mid-animation positions never register as a false scroll-up.