- We could use a different default ncols for workspaces on different outputs.
  It could be configurable and/or calculated from the dimensions of the outputs.
  E.g. three or four columns default ncols, automatically, on wider monitors.
  Possible design: --ncols-min-width=N option, incompatible with --cols.
  Then the default ncols for a workspace on an output is the output's width
  divided by N, rounded down.
