Covers onTabPress (Tab-only), preventScrollWithArrowKey (arrows-only),
onEnterOrSpace (Enter/Space gate the callback), and stopPropagation's
editable-element check (does not swallow keys when an input/textarea/
contenteditable is focused) via mock events + a document.activeElement stub.
Full suite now 133 tests.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
