Show my music on the left panel separated by album / artist / parent file

### Problem

Music on the left panel isn't separated and is ordered in chronological order of opening the file which can then be randomly shuffled

### Proposal

Music on the left should have the option to be separated by album / artist / parent file.

### Prior Art (Optional)

_No response_

Start by tracing the left-panel music list and how it currently orders files opened by the user. Review the existing UI and library structure before adding selectable album, artist, and parent-file grouping; done means each option separates the displayed music as proposed instead of relying only on chronological order.

Written by the indexing model from the issue text.