How would you create a dismissible modal dialog over the current screen?

This tests whether you treat a modal as an inert, focus-managed overlay rather than a simple pop-up layer. A strong answer covers four things in order: first, dimming the underlying screen to signal inertness; second, moving focus into the dialog on open and trapping Tab cycles inside it; third, providing visible dismissal controls and Escape support; and fourth, restoring focus to the trigger on close. Red flag: describing auto-layout and component variants while ignoring focus, keyboard trapping, and screen reader semantics.