Extract shared TimeInterval.formattedAsTimestamp replacing 8 identical
formatTime/formattedTime implementations across player views. Remove
unused currentTime parameter from GestureSeekPreviewView. Consolidate
duplicated geometry math in MacOSControlBar into seekPreviewPosition().
Extract chapter title from inside the storyboard preview into a
standalone ChapterCapsuleView with its own glass capsule background.
The capsule follows the seek position horizontally but independently
clamps to screen edges using alignmentGuide, allowing it to be wider
than the storyboard thumbnail without going offscreen.
Display a floating time pill above the seek bar during dragging
(iOS) and dragging/hovering (macOS) when video has no storyboard
thumbnails. Includes chapter name when available.
