fix(player): tell same-language subtitle rows apart across episodes

The committed track kept the server display title, which collapses to the
bare language ("English") and is identical for every same-language row: a
carried signs/songs choice tied with the full dialogue track on the next
episode and latched onto whichever row sorted first. The row's own title
is preferred now, so the carried intent names the exact row again and the
native pass can match the right container track by title instead of
language order.

Reproduced against a live library where both English ASS rows differ only
by Title ("Styled Subtitles" vs "Signs/OP/ED").

close #1785

lib/services/playback_subtitle_resolver.dart

@@ -263,7 +263,11 @@ class PlaybackSubtitleResolver {
     final playable = sidecar?.track;
     return SubtitleTrack(
       id: 'source:${sourceTrack.id}',
-      title: playable?.title ?? sourceTrack.displayTitle ?? sourceTrack.title ?? sourceTrack.language,
+      // The row's own title first: server display titles collapse to the bare
+      // language ("English") and are identical across same-language rows, so
+      // a carried intent built from them cannot tell a Signs/Songs track from
+      // the full dialogue track on the next episode (#1785).
+      title: sourceTrack.title ?? playable?.title ?? sourceTrack.displayTitle ?? sourceTrack.language,
       language: playable?.language ?? sourceTrack.languageCode ?? sourceTrack.language,
       codec: playable?.codec ?? sourceTrack.codec,
       isDefault: sourceTrack.selected,

test/services/playback_subtitle_resolver_test.dart

@@ -605,6 +605,91 @@ void main() {
       expect(result.isOff, isTrue);
       expect(result.declinedPreference, isNull);
     });
+
+    test('same-language rows are told apart by their titles across episodes (#1785)', () {
+      // Real-world shape (Madoka Magica on Plex): both rows English ASS with
+      // the bare displayTitle "English"; only Title separates the full
+      // dialogue track from the signs/songs track.
+      MediaSubtitleTrack row(int id, String title, {bool selected = false}) => MediaSubtitleTrack(
+        id: id,
+        language: 'English',
+        languageCode: 'eng',
+        title: title,
+        displayTitle: 'English',
+        codec: 'ass',
+        selected: selected,
+        forced: false,
+      );
+
+      // E1: the viewer picks the signs track and the session commits it. The
+      // committed track must keep the discriminating row title, not the
+      // language-only display title.
+      final committed = PlaybackSubtitleResolver.subtitleTrackForSource(row(53164, 'Signs/OP/ED'));
+      expect(committed.title, 'Signs/OP/ED');
+
+      // Episode boundary demotes the committed reference to its intent.
+      final carried = SubtitlePreference.demoteToIntent(SubtitlePreference.track(committed));
+
+      // E2: same pair; the dialogue row sorts first AND is server-selected —
+      // the carried signs choice must still win over both.
+      final result = PlaybackSubtitleResolver.resolve(
+        metadata: metadata,
+        mediaInfo: _mediaInfo([row(53193, 'Styled Subtitles', selected: true), row(53194, 'Signs/OP/ED')]),
+        sidecars: const [],
+        preferredSubtitleTrack: carried,
+        preserveSourceIdentity: false,
+      );
+
+      expect(result.primarySourceStreamId, 53194);
+      expect(result.declinedPreference, isNull);
+    });
+
+    test('a Jellyfin signs pick beats the server per-episode default on the next episode (#1785)', () {
+      // Verbatim shape from a live Jellyfin server (Attack on Titan): both
+      // rows English ASS, discriminated by Title, and the server names the
+      // full-dialogue row (DefaultSubtitleStreamIndex 3) on every episode.
+      MediaSourceInfo episodeInfo() => jellyfinMediaSourceToMediaSourceInfo({
+        'Id': 'src-1',
+        'DefaultSubtitleStreamIndex': 3,
+        'MediaStreams': [
+          {'Index': 1, 'Type': 'Audio', 'Language': 'jpn', 'IsDefault': true},
+          {
+            'Index': 3,
+            'Type': 'Subtitle',
+            'Language': 'eng',
+            'Codec': 'ass',
+            'Title': 'Full Subtitles',
+            'DisplayTitle': 'Full Subtitles - English - Default - ASS',
+            'IsDefault': true,
+          },
+          {
+            'Index': 4,
+            'Type': 'Subtitle',
+            'Language': 'eng',
+            'Codec': 'ass',
+            'Title': 'Signs & Songs',
+            'DisplayTitle': 'Signs & Songs - English - ASS',
+          },
+        ],
+      });
+
+      final e1 = episodeInfo();
+      final picked = e1.subtitleTracks.firstWhere((row) => row.id == 4);
+      final committed = PlaybackSubtitleResolver.subtitleTrackForSource(picked);
+      expect(committed.title, 'Signs & Songs');
+
+      final carried = SubtitlePreference.demoteToIntent(SubtitlePreference.track(committed));
+      final result = PlaybackSubtitleResolver.resolve(
+        metadata: metadata,
+        mediaInfo: episodeInfo(),
+        sidecars: const [],
+        preferredSubtitleTrack: carried,
+        preserveSourceIdentity: false,
+      );
+
+      expect(result.primarySourceStreamId, 4);
+      expect(result.declinedPreference, isNull);
+    });
   });
 
   test('selected embedded subtitle keeps sidecars out of the open', () {