OptionalbehaviorsOptionalparamsPer-binding action parameters. The action's invoker reads
these via the second arg to run (or via InvocationCtx for ongoing
invokers, when needed). Loose typing (Record<string, unknown>) for
now; consider per-action typing later via BindingOpts.
params may also be a thunk evaluated each time the
dispatcher (or invoker) needs the value. Thunks let tools close over
refs that mutate during a gesture (e.g. polygon sides adjusted
mid-drag via ArrowUp). For ongoing invokers that want the latest
values at commit, the invoker can re-call the thunk inside onEnd
via resolveParams(opts?.params).
Per-invocation options the dispatcher reads from a
GestureBinding'soptsfield and passes toOngoingInvoker.start. Today carries behaviors; extensible.