Function repository_get_series_current_episode 

pub async fn repository_get_series_current_episode(
    manager: State<'_, RepositoryManagerWrapper>,
    handle: String,
    series_id: String,
) -> Result<Option<MediaItem>, String>

The episode a viewer should land on when they open a series.

“Current” is domain policy, not layout: an episode in progress, else the server’s Next Up for the series, else the first unwatched episode, else the first. The third rung is what makes this work offline, where Next Up is always empty. Returns None only when the series has no episodes at all.

TRACES: UR-062 | DR-101