Accessibility
Fieldset with a required legend so the collection exposes a single group name. Each key is a button with aria-label from keyLabels; visible symbols stay on screen for sighted users. The zero key adds aria-description from optional zeroHoldForPlusDescription or the package default for the hold-for-plus action.
Typed digits, *, #, and plus while focus is inside the grid trigger the same handler as a click, without modifier keys. Long press on zero or a held Enter or Space on focused zero emits plus once.