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>

CHANGELOG.md

@@ -2,6 +2,8 @@
 
 ## Unreleased
 
+- **Cast in the details pane:** with a Trakt client ID, the details of a movie or series list its
+  director (or creators) and cast with their roles below the plot, in every view.
 - **Enter adds** a title in Movies and Series; `a` no longer does (the status bar only ever named
   Enter, and the hint for searching releases of a title not in the library now says Enter too).
 - **Trending, most watched and anticipated** movies and series from Trakt: with an empty search