OptionalextendDefault 'shift'. Ignored in single-mode.
OptionalinitialDefault [].
OptionallockWhen true, every mutator (set/add/remove/toggle/clear/
applyClick) is a no-op — selection stays at whatever initial
pinned it to. Useful for demos that exist to showcase a single
pre-selected node (e.g. the bezier-edit curve) and don't want a
stray click to deselect.
OptionalmodeDefault 'single'.
Options for useSelection.