Half-circle page-number tab centered on the bottom edge, from the approved Nashville PBS report layouts.

```jsx
<div style={{ position: "relative", width: 816, height: 1056 }}>
  ...
  <PageTab>8</PageTab>                                     {/* white page */}
  <PageTab tone="var(--white)" ink="var(--pbs-blue)">6</PageTab>  {/* blue page */}
</div>
```
Width 72px on a Letter page (height is half). Content pages carry the tab; covers and pillar dividers do not.