UAT found a dead end: F -> YouTube's fullscreen button -> Esc left the player
maximised with no way back, and a further F produced a second, control-less
fullscreen with the wheel driving YouTube's own volume box.
Measured cause: reaching YouTube's control bar means clicking INTO the player,
which moves keyboard focus into the cross-origin iframe — and it stays there.
Our window-level shortcuts then never fire (document.activeElement === IFRAME),
so F went to YouTube instead of toggling our maximise.
Fix: on fullscreenchange, when fullscreen ends, focus the modal card again.
Verified in real Chrome, step by step:
- F -> maximised, no browser lock, focus on our card
- YouTube's own FS button -> real fullscreen (innerHeight 889 -> 1024)
- leaving fullscreen -> focus back on our card (was: still the iframe)
- F -> back to the normal modal view (was: a second fullscreen with no controls)
peter
aae37591cb