Details pane: director and cast from Trakt

With a Trakt client ID, the details of a movie or series show the
director(s) or creators and up to 8 cast members with their roles below
the plot, in every view. The title is found on Trakt by its TMDb/TVDB
(else IMDb) id, then its people are read. Casts are cached and, like
posters, only loaded once the selection rests.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

internal/ui/episodes.go

@@ -294,7 +294,7 @@ func seriesRowDetail(s sonarr.Series, ep *sonarr.Episode, season int, sum season
 			plot = tview.Escape(ep.Overview)
 		}
 	}
-	return detailText{head: head, plot: plot}
+	return detailText{head: head, plot: plot, people: seriesRef(s)}
 }
 
 // enter expands or collapses a season, or opens the release search for an episode.