docs(jellyfin): the art delivery result, and what stays blank on purpose

serverAppConfigs-docs/Dankserver/Jellyfin.md

@@ -87,7 +87,9 @@ poster list even with every automatic pass switched off — plugin, key and CDN
 proven by that one response — so a refresh that stores nothing beside it is a
 library-switch problem, never a provider problem. It is also the delivery door:
 `POST /Items/{id}/RemoteImages/Download` saves the chosen image to the internal
-store on a build where the automatic image pass will not run at all.
+store on a build where the automatic image pass will not run at all — it is how
+the Movies library got its art: 2,515 of 2,564 films carry a primary now, and the
+rest have none in TMDb (shorts like `Astartes`, files whose names match nothing).
 
 **API shape on 12.x:** `/Items` and `/Items/{id}` need `UserId` when
 authenticated by API key — without it the answer is `400 Error processing