The README screenshot shows a UI nostui no longer has

Noticed while reviewing #528.

`screenshot.gif`, embedded at the top of the README, is the first thing anyone sees on GitHub. Its first frame reads:

```
0.00 ticks per sec (app) 0.00 frames per sec (render)
```

Two versions out of date at once. The two-number form was replaced by "X.XX ticks per sec" earlier in this release cycle, and #528 removes the counter and its row altogether — so the gif advertises a UI element that no longer exists, in a form that already did not exist.

It is stale independently of that: the gif shows a tab labelled `Timeline`, where the code now renders `Home`.

This needs a re-recording rather than an edit, which is why #528 left it alone.

## Acceptance

- The screenshot shows the current layout: no FPS row, and the tab bar on the top line.