Introduces a "Display sections as" picker in Home settings with List and
Grid modes. Grid renders each section as a horizontal shelf of video
cards, defaulting to Grid on tvOS and List on iOS/macOS. Per-platform
defaults are preserved via a platform-specific settings key.
On tvOS the shelf is a focus section so swiping up/down between rows of
different lengths works without getting stuck at the end of a row.
Post watchHistoryDidChange notification when a new watch entry is inserted
during local playback progress updates (but not on every progress tick).
Reload Home data when switching back to the Home tab and when the Customize
Home sheet is dismissed.
