ReadonlyaltReadonlycodeReadonlyctrlReadonlykeyReadonlymetaReadonlyshiftOptional ReadonlytargetThe event's origin (the focused element the keystroke was delivered to) — read by the origin-containment rule (see KeyBindingDispatcher.dispatch). Optional: a caller that can't supply one (a hand-built test event) is treated as unrestricted.
The minimal keyboard-event shape KeyBindingDispatcher.dispatch needs. Satisfied by BOTH a native
KeyboardEvent(the KeyBindingDispatcher.attach path, for generic regions) and a ReactKeyboardEvent(the grid's synthetic terminal-tap path) — so the grid can stay on one event system instead of mixing a native listener into its synthetic Stage dispatch.