Workspaces should have a visual saved/save failed/needs save indicator

Similar to the red rimmed screen in the OE. When I save a world, I need to watch for the popup to show up in the bottom right to know whether it worked or not; what I'd like is an indicator that is more persistent and where any failure is easier to trace.

Start by tracing the workspace save flow and the existing bottom-right save popup mentioned in the issue. Define a persistent indicator for saved, save failed, and needs save states, with failures easier to trace; the work is done when those states remain visible without relying on the popup.

Written by the indexing model from the issue text.