The large-logical-iframe + CSS-scale-down trick to force a 1080p start did not
work behind the user's work VPN (YouTube caps quality by network there regardless
of viewport size), and the two-phase native switch could downgrade a latched
1080p to 480p on some streams. Not worth the complexity for an unreliable win —
revert to the original "opens at whatever resolution YouTube picks" behaviour;
the user sets 1080p manually via fullscreen + the gear as before.
Kept: the windowed maximise (fullscreen) button added to the player meta row.