A hidden backface still hit-tests in Chrome, so after flipping a card
the front's picture-in-picture sat invisibly over the back's chips,
showing its zoom cursor and eating the flip-back click. Pointer events
now follow visibility: the back is inert until the card flips, and the
front goes inert while it is flipped.
Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>