This puts the 3 utility windows at the top, horizontally split, with the
code view below. The terminal window is drawn either vertically split
(if there's room) or horizontally split otherwise. The output window
remains at tht bottom.
We add equivalent sizing options too, setting some defauts that roughly
work on my macbook pro.
By default we switch to the narrow layout if there are fewer than 160
columns, but this can be overridden by setting g:vimspector_ui_mode.
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