The original icon fix assumed that the `<svg>` tag had an `alt` attribute, which it does not. Instead, SVG requires a child element to specify a description. A complete fix involves patching upstream to allow for setting this element, but since we don't seem to have actionable icons without associated textual controls, set `aria-hidden="true"` by default and require it to be overridden if needed.
* Make `<main>` the part of the page that actually changes when the route updates, thus making navigation to page content easier.
* Add labelled region for persistent audio player.
This matches better with adding alt text to images, which is probably better than either manually opting out of the accessibility tree or creating some less-compatible implementation.