A saved streaming-services preference drives a personalized 'On your streaming services' rail:
- GET/POST /discover/providers-pref (TMDB provider ids); /discover/list OR-joins multiple
providers (comma->pipe) into with_watch_providers.
- A 📺 multi-select in the toolbar (Netflix/Prime/Disney+/Max/Apple TV+/Hulu/Paramount+/Peacock);
selecting services saves the preference and rebuilds the rails.
- The rail (high priority, after taste) appears once you've picked services, showing what's
streaming on yours.