fix(playback): apply default quality to jellyfin

close #1150

lib/media/media_server_client.dart

@@ -506,7 +506,7 @@ abstract class MediaServerClient {
   /// playback. Backends own the per-backend particulars: Plex runs the
   /// transcode-decision flow when [PlaybackInitializationOptions.qualityPreset]
   /// is non-original; Jellyfin asks PlaybackInfo for a matching stream when a
-  /// non-original preset is explicitly selected. Throws
+  /// non-original preset is selected. Throws
   /// [PlaybackException] when the item can't be resolved (no MediaSources,
   /// no playable URL, transcode decision unavailable).
   ///

lib/models/transcode_quality_preset.dart

@@ -1,8 +1,8 @@
 /// Video transcode quality presets modeled on Plex Web's custom-quality table.
 ///
-/// When a non-[original] preset is selected, playback goes through Plex's
-/// `/video/:/transcode/universal/decision` + `start` flow. [original] bypasses
-/// transcoding entirely and uses the direct-play URL.
+/// When a non-[original] preset is selected, playback asks the active backend
+/// for a capped transcode stream. [original] bypasses transcoding entirely and
+/// uses the direct-play URL.
 enum TranscodeQualityPreset {
   original(null, null, null),
   p240_320(320, '420x240', 30),

lib/screens/video_player_screen.dart

@@ -609,12 +609,12 @@ class VideoPlayerScreenState extends State<VideoPlayerScreen> with WidgetsBindin
           throw StateError('No client registered for ${_currentMetadata.serverId}');
         }
         _streamHeaders = genericClient.streamHeaders;
-        // Single source of truth for showing quality controls. Plex uses a
-        // per-server probe; Jellyfin supports explicit quality selection but
-        // should not inherit the global Plex-style default on ordinary play.
+        // Single source of truth for showing quality controls and applying the
+        // saved startup quality. Backends that cannot transcode always start at
+        // Original even if the user picked a lower default quality.
         _serverSupportsTranscoding = genericClient.capabilities.videoTranscoding;
         if (widget.selectedQualityPreset == null) {
-          _selectedQualityPreset = genericClient.backend == MediaBackend.plex && _serverSupportsTranscoding
+          _selectedQualityPreset = _serverSupportsTranscoding
               ? settingsService.read(SettingsService.defaultQualityPreset)
               : TranscodeQualityPreset.original;
         } else {