Stand the screen's key bindings down while a checkbox has focus.
The screen-level enter/up/down/tab bindings are priority, so
without this gate they consume the key before the focused Checkbox
can use it: Enter/Space must toggle (Textual binds them on
ToggleButton), and up/down/tab must step between checkboxes.
Returning False disables the screen binding for that dispatch so
the key reaches the checkbox / focus system.
The action name being dispatched.
The action's parameters.
