ProgressBar

Pass `value` for a determinate fill, `busy` for work in flight, `indeterminate` for open-ended progress, or `count` for segment accumulation. `busy` and `indeterminate` are different claims: `indeterminate` means UNBOUNDED and draws a static dotted line, while `busy` means LOADING and sweeps an accent band over the track – pair `busy` with a `value` for a run whose stages are only partly countable, so the bar holds its fill through the stage that cannot report a count. Use `label` to expose role="progressbar", or `decorative` when adjacent text already conveys the value. It renders as spans, so it is valid inside a button, which is how the TabBar underline works.