Ref T12738. This is mostly just laying in groundwork and prerequisites, like the ability to query items by queue.
Eventually, this will become the main UI which staff use to process a queue of items. For now, it does nothing and renders nonsense.
This and probably the next big chunk of changes are all going to be made-up, nonfinal things that just make basic operations work until we have fundamental flows -- like "assign", "comment", "close" -- working at a basic level and can think more about UI/workflow.