**ProgressBar** — slim bar for library scans, playout builds and transcodes. Omit `value` for an indeterminate sweep (queued/starting work).

```jsx
<ProgressBar value={62} showLabel />
<ProgressBar value={null} tone="accent" /> {/* scanning… */}
```

Props: `value` (0–100 or null), `tone` (accent·ok·warn·error), `height`, `showLabel`.
