Feature: Enable a mechanism to show/hide captions on-demand

Currently, there is a possibility to autoplay a muted video with a captions track shown. However, there is no way to, for instance, hide those captions if user disables `muted`.

Since the video is behind and iframe, there is no way to access to the `tracks` and hide them using something like

```js
videoRef.textTracks[0].mode = 'hidden'
```

Start by tracing the iframe integration and the existing muted, autoplay, and captions behavior. Determine how the component can expose caption visibility when the user changes muted state, then verify that captions can be shown and hidden on demand without direct access to the iframe's textTracks.

Vom Indexierungsmodell aus dem Issue-Text verfasst.