Add audio-only music mode

Persistent per-platform mode that plays only the audio track to save
bandwidth and speed up loads. When enabled, stream selection picks the
best audio-only stream (preferred language, codec, bitrate) and never
fetches the video URL; toggling mid-video reloads at the current
position using the quality-switch path (live vid=no toggling is avoided
due to A/V desync).

- Toggle row in the player quality/settings sheet on iOS, macOS and
  tvOS, next to lock controls
- New audioMode control button type (red when active) for player
  controls and mini player layouts
- Picking a video quality explicitly turns the mode off; audio track
  picks keep it on and now work while audio-only is playing
- Stream URL refresh preserves audio-only playback instead of
  resurrecting video
- Queue preloads and history entries resolved before a toggle are
  discarded so selection re-runs with the current mode
- tvOS player shows the video thumbnail instead of a black screen
  during audio-only playback
- PiP button hidden for audio-only streams

Yattee/Views/Player/QualitySelectorView+Sections.swift

@@ -323,14 +323,22 @@ extension QualitySelectorView {
     @ViewBuilder
     var generalSectionContent: some View {
         #if os(tvOS)
-        // tvOS only has the speed row here; style it to match the Settings rows.
-        playbackSpeedRow
+        // tvOS rows are styled individually to match the Settings rows.
+        VStack(spacing: 8) {
+            playbackSpeedRow
+
+            audioModeRow
+        }
         #else
         VStack(spacing: 0) {
             playbackSpeedRow
 
             Divider()
 
+            audioModeRow
+
+            Divider()
+
             lockControlsRow
         }
         .cardBackground()
@@ -408,6 +416,45 @@ extension QualitySelectorView {
         #endif
     }
 
+    @ViewBuilder
+    private var audioModeRow: some View {
+        #if os(tvOS)
+        Button {
+            onAudioModeToggled?(!isAudioMode)
+        } label: {
+            HStack {
+                Label(String(localized: "player.quality.audioMode"), systemImage: "music.note")
+                    .font(.headline)
+
+                Spacer()
+
+                Text(isAudioMode ? String(localized: "common.on") : String(localized: "common.off"))
+                    .foregroundStyle(.secondary)
+            }
+            .padding(.vertical, 14)
+            .padding(.horizontal, 20)
+            .frame(maxWidth: .infinity, alignment: .leading)
+            .contentShape(Rectangle())
+        }
+        .buttonStyle(TVSettingsRowButtonStyle())
+        #else
+        HStack {
+            Label(String(localized: "player.quality.audioMode"), systemImage: "music.note")
+                .font(.headline)
+
+            Spacer()
+
+            Toggle("", isOn: Binding(
+                get: { isAudioMode },
+                set: { onAudioModeToggled?($0) }
+            ))
+            .labelsHidden()
+        }
+        .padding(.vertical, 12)
+        .padding(.horizontal, 12)
+        #endif
+    }
+
     #if !os(tvOS)
     @ViewBuilder
     private var lockControlsRow: some View {
@@ -751,7 +798,11 @@ extension QualitySelectorView {
 
     private func handleAudioStreamTap(_ stream: Stream) {
         selectedAudioStream = stream
-        if let video = selectedVideoStream, video.isVideoOnly {
+        if currentStream?.isAudioOnly == true {
+            // Audio mode / audio-only content: the tapped track IS the main stream
+            onStreamSelected(stream, nil)
+            performDismiss()
+        } else if let video = selectedVideoStream, video.isVideoOnly {
             onStreamSelected(video, stream)
             performDismiss()
         }