A Workspace is built by folding two together, but there was no single
move that took one back apart — you dragged each pane out to the
Navigator one at a time, and the last one could not be dragged out at
all, because a pane alone in its Workspace has nothing to detach from.
Separate Panes on a merged Workspace's row is the inverse of merge: one
Workspace per pane, in layout order, sessions untouched.
The status bar was a docked strip with a hairline above it, reading as
window chrome bolted under the content. It is a glass capsule now,
floating in the trailing corner of the pane it describes. It hugs its
text rather than spanning the width — a full-width bar over a terminal
covers whole lines of output, and the prompt is on the left — and stops
growing at `maxWidth` so a deep working directory truncates instead.
Floating means it no longer takes layout space, so switching to a
Workspace stops resizing the content area. It also means it sits over the
pane, so the command generator and the upload notices now clear it by
`StatusBar.overlayClearance` — a constant rather than a measurement, and
applied whether or not the capsule happens to be showing, because a
notice that moves depending on whether a transfer is running is worse
than one that is always in the same place.
844 tests pass.