Restyle and relayout the back/forward arrows

Right now back/forward arrows are a little non-obvious. I want to make them bigger and more obvious. Having them take up the entire width of the aside makes sense to me. In rudimentary diagram:

```
------------|
header |
------------|
| problem |
| text |
| |
| |
| |
|-----------|
| < | > |
------------|
footer |
------------|

```

Start by locating the frontend component that renders the back and forward arrows and inspect the current aside layout. Done means the arrows are larger, more obvious, and occupy the aside's full width in the two-button arrangement shown in the issue diagram.

Written by the indexing model from the issue text.