Cross-boundary focus arrival picked the structural leftmost/rightmost
container, ignoring layout_flip. Since layout_flip mirrors geometry
without reordering containers, focusing into a horizontally-flipped
workspace landed on the far edge instead of the container at the edge
the user crossed toward, while intra-workspace focus (via
OperationDirection::destination) already accounts for the flip.
Extract OperationDirection::cross_boundary_edge_index, which picks the
edge index against the flipped direction like destination() does, and
use it at the eight focus-arrival call sites. Add a komorebi-layouts
test that checks the pick against the rendered rectangles.
Reactive events pass trigger_focus=false so komorebi follows the OS
foreground and reconciles via the FocusChange handler once Windows
promotes a successor window. When the destroyed window was the
foreground and Windows promotes nothing, the foreground becomes null,
no FocusChange arrives, and komorebi's selection never regains OS focus,
leaving every border unfocused until the user refocuses by hand.
Add a narrow fallback in the Destroy/Unmanage handler: when the OS
foreground is null after removal, focus the current selection. Any
non-null foreground is left to FocusChange, so the OS is not fought and
the should_skip_focus_change desync cannot occur.
Matt Kotsenas