webclient: one audio player, so a published card sounds like the viewer ...

The published-content card fell back to the browser's own grey bar while the
full-screen viewer had a player with the track's name, times, seek and
volume. The card now shows that player too, tightened a little for a body
that sits under a summary row.

The player moved out of ContentLightbox unchanged: two copies would have
drifted, and it is the same file in both places.