React-side extension of SequenceOptions: an optional ref to a
DOM element that doubles as a mouse region. When a ref and a focusId
are both present, useKeyboard().boundSequence records the
ref → focusId mapping so that clicking the region (via useMouseRegion)
forwards keyboard focus to focusId.
React-side extension of SequenceOptions: an optional ref to a DOM element that doubles as a mouse region. When a
refand afocusIdare both present,useKeyboard().boundSequencerecords the ref → focusId mapping so that clicking the region (viauseMouseRegion) forwards keyboard focus tofocusId.