Previously a failed video left the user staring at a black screen / thumbnail
with no indication anything went wrong — playbackState went to .failed but
TVPlayerView never read it. Add a focusable glass overlay (Details / Retry /
Play Next or Close) gated on isFailed and a parallel one for retry-exhausted
state, with the regular controls and background tap-target disabled while
either is visible so focus stays inside the overlay. Hide the Copy/Share
toolbar items in ErrorDetailsSheet on tvOS where they aren't useful.
