message: don't overlay above right pane
  fixes:
diff: .right-pane-visible .shell-pane-left
  .right-pane-visible .shell-sidebar
  -.left-pane-visible .shell-pane-right
  z-index: $zindex-shell-pane-under !important
  // When we are hiding the pane and showing the content again, we want to also
  