ReadonlyaltWhether Alt was held.
ReadonlycodeThe physical key, layout-independent — "KeyA", "Space".
ReadonlyctrlWhether Control was held.
ReadonlykeyThe character or named key produced — "a", "Enter", " ".
ReadonlymetaWhether Meta (Command, Windows) was held.
ReadonlyrepeatWhether the platform's auto-repeat produced this event.
ReadonlyshiftWhether Shift was held.
The one thing a SceneKeyEvent needs from the platform event behind it: a way to suppress the host's own reaction to the keystroke.
Structural and optional, for this package's usual reason — a browser
KeyboardEvent, a Playwright-synthesized one, and a plain object in a unit test are all equally acceptable, and namingKeyboardEventwould pull a DOM lib into a package that must build in Node.