The Unified Banner's discard confirmation dialog now creates Ink

buttons instead of input-based buttons, ensuring we have a consistent

style for the dialog.
One notable difference in behavior is that Ink buttons don't propagate

click events when an onClick handler is registered, so we now need to

ensure we close the dialog when clicked.

Tested the dialog on light and dark mode.
Tested both the Cancel and Discard buttons, making sure that Cancel closed

the dialog and Discard correctly discarded and reloaded the page.