The track identity competes with the transport for the footer's one band

[thcp]

The problem

The footer has to be two things at once, and the library column beside it has
room to spare.

The footer's left column holds what is loaded: cover, title, duration, stem
count, source, extraction date, favourite and Export Mix. The rest of the footer
holds how it plays: transport, position, speed, key, click track, timeline.
Those are different questions, and the identity block wins a 300 px column
of the footer to answer one of them.

Meanwhile the library sidebar, which is where the user is already looking to
choose a track, ends in whitespace below its last section.

The navigation order

A smaller thing in the same column. The rail reads Library, Favorites, Trash,
Queue. Queue is an active, transient state and sits below Trash, which is an
archive. The order does not match how often the four are used or how they relate.

Constraints

• The footer's timeline has to keep its left offset regardless of what happens to
  the identity block, because it lines up with the lane waveforms.
• Whatever holds the track identity has to stay visible while the library list
  scrolls: it describes the loaded track, not the list.
• The export menu opens upward out of its own box, so nothing on its ancestor
  path may clip.
• Collapsing the library hides the whole sidebar body, so anything moved there
  goes with it.