Maps action IDs to the normalized keys that trigger them (for stopAction).
Keys allowed to pass through a modal barrier while this focus target is active.
Registered key bindings (evaluation order).
Key rules marked as transparent on this target (pass-through).
OptionalrefNumber of live bindings holding this target.
Only maintained when the engine runs with releaseFocusWhenEmpty; the
target is removed once the last holder releases it (see
LayerManager.releaseFocus). Optional so the exported type stays
backwards compatible — the engine always initializes it.
Key rules stopped on this target (propagation barrier).
Focus target state for a page (screen) layer.