Handle which elements are focusable

Calling `focus` on an element is AFAIK a little more involved than currently implemented.

AFAIK, the closest focusable parent element should be the target of focus.

Research, and validate assumptions.

No file, test, or entry point is named in the issue. Research the rules for focusable elements and validate whether the closest focusable parent should receive focus, then identify the relevant implementation and tests; done means the behavior and assumptions are covered by tests.

Written by the indexing model from the issue text.