Non-exhaustive enums could have additional variants added in future. Therefore, when matching against variants of non-exhaustive enums, an extra wildcard arm must be added to account for any future variants.
Carve out a fixed n-cell gap between every adjacent pair of panes. The gap comes out
of the area before constraints are resolved, so Fill/
Percent panes share only what’s left after every gap is
reserved. No-op with fewer than two panes or n == 0.
Shift every pane back by n cells so it overlaps the trailing edge of the previous
pane, e.g. so two adjacent bordered panels can share one line of border instead of each
drawing its own (ratatui’s Spacing::Overlap). Purely geometric: retroglyph does not
merge the overlapping cells’ contents, so whichever pane is drawn last wins on the
shared cells. No-op with fewer than two panes or n == 0.