Fixed two playback bugs in reverse (↑) mode:

• Skipped videos: with reverse enabled, finishing a video could advance two
items up instead of one, skipping every other video while climbing the
playlist. Each video end now advances exactly one item.

• Frozen playback: after the extension navigated to the previous item, the
arriving video could occasionally refuse to play (stuck at its beginning).
The internal playback hold now always releases within 3 seconds even when
YouTube's navigation-finished signal is missed.

No changes to permissions (the extension still requests none), no new
features, and no data collection.

Release Notes:

• Fixed a brief playback flash that could occur before navigation completed during ordinary reverse-order hops.
• Improved top-of-playlist behavior: with Loop disabled, playback now remains on the first item and displays YouTube’s native end screen.
• With Loop enabled, playback correctly wraps from the first item to the final playlist item.
• Improved compatibility and stability with YouTube’s player behavior.