Swap shows only the new media, no guessed endings, quieter screen

- A swap stops the previous media at once; buffer counts only for the
  media the player holds (client) and the current mediaId (server), so
  the old video can no longer start the new one.
- The automatic frozen-picture reload is gone (false alarms on still
  scenes); Reload video stays.
- The "Next episode" pill shows only from a known ending.
- A web link's thumbnail is its cover, under the video's own name.
- While playing, the unread chip stays off the picture; chat pop-ups
  can be All / Only when paused / Off.
- Server fetch failures say when the server has no cookies.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

apps/desktop/lib/src/playback/frame_watchdog.dart

@@ -1,120 +0,0 @@
-import 'dart:typed_data';
-
-/// FNV-1a over a 15x15 grid of RGB(A) pixels in the central half of an
-/// image. Used on a small capture of what the compositor shows: the
-/// centre is video, the edges carry the (changing) control overlays.
-int hashCenterPixels(ByteData rgba, int width, int height) {
-  var x = 0x811c9dc5;
-  if (width <= 0 || height <= 0) return x;
-  for (var gy = 1; gy < 16; gy++) {
-    for (var gx = 1; gx < 16; gx++) {
-      final px = (width * (0.25 + 0.5 * gx / 16)).floor();
-      final py = (height * (0.25 + 0.5 * gy / 16)).floor();
-      final o = (py * width + px) * 4;
-      if (o + 3 > rgba.lengthInBytes) continue;
-      for (var c = 0; c < 3; c++) {
-        x = ((x ^ rgba.getUint8(o + c)) * 0x01000193) & 0xffffffff;
-      }
-    }
-  }
-  return x;
-}
-
-/// FNV-1a over ~4k bytes spread evenly across a raw frame (mpv
-/// `screenshot-raw`); dimension-agnostic, enough to tell frames apart.
-int hashSpread(Uint8List bytes) {
-  var x = 0x811c9dc5;
-  if (bytes.isEmpty) return x;
-  final step = bytes.length <= 4096 ? 1 : bytes.length ~/ 4096;
-  for (var i = 0; i < bytes.length; i += step) {
-    x = ((x ^ bytes[i]) * 0x01000193) & 0xffffffff;
-  }
-  return x;
-}
-
-/// One sample of player state, taken about once a second.
-class FrameSample {
-  final DateTime at;
-  final double position;
-
-  /// Fingerprint of the picture currently shown on screen; null when it
-  /// cannot be captured (no view, hidden window, headless).
-  final int? frames;
-
-  /// Playing, not buffering, rate > 0, video track present, window
-  /// visible. Anything else disarms the watchdog.
-  final bool eligible;
-  const FrameSample({
-    required this.at,
-    required this.position,
-    required this.frames,
-    required this.eligible,
-  });
-}
-
-/// Detects a frozen picture: position advances normally but the shown
-/// picture stands still for [stallAfter]. Seeks (position jumps), pauses,
-/// buffering and missing captures all reset the stall clock. A hit is a
-/// suspicion only — a still scene looks the same — so the caller confirms
-/// it against the decoder and calls [dismiss] when it was a still scene.
-/// Fires at most once until the picture is seen moving again for
-/// [rearmAfter], so a player that stays (or soon gets) frozen after a
-/// reload does not reload in a loop. [reset] keeps that latch.
-class FrameWatchdog {
-  static const stallAfter = Duration(seconds: 3);
-  static const rearmAfter = Duration(seconds: 10);
-
-  FrameSample? _last;
-  DateTime? _stallSince;
-  DateTime? _healthySince;
-  bool _fired = false;
-
-  void reset() {
-    _last = null;
-    _stallSince = null;
-    _healthySince = null;
-  }
-
-  /// The last hit was a still scene: re-arm, but wait a full
-  /// [stallAfter] before suspecting again.
-  void dismiss() {
-    _fired = false;
-    _stallSince = null;
-  }
-
-  /// Returns true exactly when a freeze is suspected.
-  bool feed(FrameSample s) {
-    final last = _last;
-    _last = s;
-    if (!s.eligible || s.frames == null || last == null ||
-        !last.eligible || last.frames == null) {
-      _stallSince = null;
-      _healthySince = null;
-      return false;
-    }
-    if (s.frames != last.frames) {
-      _stallSince = null;
-      _healthySince ??= last.at;
-      if (s.at.difference(_healthySince!) >= rearmAfter) _fired = false;
-      return false;
-    }
-    _healthySince = null;
-    final wall = s.at.difference(last.at).inMilliseconds / 1000.0;
-    final moved = s.position - last.position;
-    // Normal playback only: a jump (seek) or a standstill (stall, the
-    // position itself stuck) is not a frozen picture.
-    final normal = wall > 0 && moved > wall * 0.5 && moved < wall * 2 + 0.5;
-    if (!normal) {
-      _stallSince = null;
-      return false;
-    }
-    _stallSince ??= last.at;
-    if (_fired) return false;
-    if (s.at.difference(_stallSince!) >= stallAfter) {
-      _fired = true;
-      _stallSince = null;
-      return true;
-    }
-    return false;
-  }
-}

apps/desktop/lib/src/playback/playback_controller.dart

@@ -16,7 +16,6 @@ import '../shaders/shader_presets.dart';
 import '../state/settings.dart';
 import '../sync/state_diff.dart';
 import '../sync/user_seek.dart';
-import 'frame_watchdog.dart';
 import 'media_marks.dart';
 import 'yt_dlp_app.dart' show AppYtDlp, ytdlFormat;
 
@@ -41,9 +40,6 @@ class PlaybackController {
 
   SyncPlayer? _player;
   VideoController? _video;
-  Timer? _watchTimer;
-  bool _probing = false;
-  final FrameWatchdog _watchdog = FrameWatchdog();
   StreamSubscription<PlayerLog>? _logSub;
   final List<StreamSubscription<Object?>> _timeSubs = [];
   String _chapterJson = '';
@@ -60,9 +56,6 @@ class PlaybackController {
   /// otherwise, so no texture outlives its player.
   final alive = signal(false);
 
-  /// Called once when the watchdog sees a frozen picture.
-  void Function()? onFrozen;
-
   /// mpv's yt-dlp hook could not open the current link (its error text).
   void Function(String error)? onYtdlError;
 
@@ -109,10 +102,6 @@ class PlaybackController {
   Player? _ytdlSetOn;
   String _ytdlRaw = '';
 
-  /// Fingerprint of the picture on screen, installed by the video view
-  /// (`ShownFrameProbe.sample`). Without it the watchdog stays idle.
-  Future<int?> Function()? shownFrame;
-
   Player get player => _player!;
 
   /// Seeks from the video controls (seek bar) go here instead of to mpv.
@@ -217,8 +206,6 @@ class PlaybackController {
     await _pinBufferProps();
     await _pin('volume-max', '$maxVolume');
     await applyShaders();
-    _watchdog.reset();
-    _watchTimer = Timer.periodic(const Duration(seconds: 1), (_) => _watch());
     generation.value++;
     alive.value = true;
   }
@@ -439,73 +426,6 @@ class PlaybackController {
     }
   }
 
-  /// Fingerprint of the decoder's current frame (mpv `screenshot-raw`,
-  /// off-thread); null without video.
-  Future<int?> _sourceFrame(Player p) async {
-    try {
-      final raw = await p.screenshot(format: null);
-      return raw == null || raw.isEmpty ? null : hashSpread(raw);
-    } catch (_) {
-      return null;
-    }
-  }
-
-  /// A suspected freeze is real only if mpv's own frames still move: a
-  /// still scene looks frozen on screen too.
-  Future<bool> _sourceMoving(Player p) async {
-    final a = await _sourceFrame(p);
-    await Future.delayed(const Duration(milliseconds: 500));
-    if (!identical(p, _player) || !p.state.playing) return false;
-    final b = await _sourceFrame(p);
-    return a != null && b != null && a != b;
-  }
-
-  static bool get _windowVisible {
-    try {
-      final s = WidgetsBinding.instance.lifecycleState;
-      return s == null ||
-          s == AppLifecycleState.resumed ||
-          s == AppLifecycleState.inactive;
-    } catch (_) {
-      return false;
-    }
-  }
-
-  Future<void> _watch() async {
-    final p = _player;
-    final probe = shownFrame;
-    // Only meaningful once the video view is up.
-    if (p == null || _video == null || probe == null || _probing) return;
-    _probing = true;
-    try {
-      final frames = await probe();
-      if (!identical(p, _player)) return;
-      final s = p.state;
-      final eligible = s.playing &&
-          !s.buffering &&
-          !s.completed &&
-          s.rate > 0 &&
-          (s.width ?? 0) > 0 &&
-          _windowVisible;
-      final fired = _watchdog.feed(FrameSample(
-        at: DateTime.now(),
-        position: positionSecs,
-        frames: frames,
-        eligible: eligible,
-      ));
-      if (fired) {
-        if (await _sourceMoving(p) && identical(p, _player)) {
-          debugPrint('video watchdog: picture stuck while mpv frames move');
-          onFrozen?.call();
-        } else {
-          _watchdog.dismiss();
-        }
-      }
-    } finally {
-      _probing = false;
-    }
-  }
-
   /// Opens [url] paused. [headers] go with every request for it (mpv
   /// `http-header-fields`): a Jellyfin token travels there, not in the URL.
   Future<void> openUrl(String url, {Map<String, String>? headers}) async {
@@ -689,8 +609,6 @@ class PlaybackController {
   Future<void> dispose() async {
     final p = _player;
     if (p == null) return;
-    _watchTimer?.cancel();
-    _watchTimer = null;
     await _logSub?.cancel();
     _logSub = null;
     for (final sub in _timeSubs) {