Sounds: Japanese-house sound set in the app, layout demo removed

Eleven sounds for events that carry news (ready, unready, everyone ready,
join, leave, kick, new video, others' chat, idle warning, connection
lost/back); none for what the video already says. New voices: koto
(Karplus-Strong, bendable), furin chime, rin bowl, bamboo, hyoshigi,
shoji slide, in the Yo scale on D. Played by SynthSfx at the Settings
volume with per-sound switches and previews. The debug layout mock is
gone.

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

apps/desktop/lib/src/shell/settings_tab.dart

@@ -1,3 +1,5 @@
+import 'dart:async';
+
 import 'package:flutter/material.dart';
 import 'package:signals/signals_flutter.dart';
 
@@ -7,7 +9,11 @@ import '../jellyfin/accounts_panel.dart';
 import '../schedule/animeflow.dart';
 import '../screens/home/about_page.dart';
 import '../screens/home/settings_page.dart';
+import '../sfx/sfx.dart';
+import '../sfx/sound_bank.dart';
+import '../sfx/synth_sfx.dart';
 import '../state/session_state.dart';
+import '../state/settings.dart';
 import '../update/update_controller.dart';
 import 'avatar.dart';
 import 'motion.dart';
@@ -431,11 +437,78 @@ class NotificationsInfo extends StatelessWidget {
             ],
           ),
         ),
-        SettingsPanel(
-          title: 'Sounds',
-          child: line('No sounds yet', 'The app is silent; only the video makes noise'),
-        ),
+        const SettingsPanel(title: 'Sounds', child: SoundSettings()),
       ],
     );
   }
 }
+
+/// Volume, then every sound with a preview button and its own switch.
+class SoundSettings extends StatelessWidget {
+  const SoundSettings({super.key});
+
+  void _preview(SfxKind kind) {
+    final sfx = SessionState.instance.sfx;
+    if (sfx is SynthSfx) unawaited(sfx.preview(kind, readyIndex: 2));
+  }
+
+  @override
+  Widget build(BuildContext context) {
+    final s = AppSettings.instance;
+    final scheme = Theme.of(context).colorScheme;
+    final muted = TextStyle(color: scheme.onSurfaceVariant, fontSize: 12);
+    return SignalBuilder(builder: (context) {
+      final volume = s.soundVolume.value;
+      final off = s.soundsOff.value;
+      return Column(
+        crossAxisAlignment: CrossAxisAlignment.stretch,
+        children: [
+          Row(
+            children: [
+              Icon(volume == 0 ? Icons.volume_off_outlined : Icons.volume_down_outlined,
+                  color: scheme.onSurfaceVariant),
+              Expanded(
+                child: Slider(
+                  key: const ValueKey('sound-volume'),
+                  value: volume,
+                  onChanged: s.setSoundVolume,
+                  onChangeEnd: (_) => _preview(SfxKind.ready),
+                ),
+              ),
+              SizedBox(width: 44, child: Text('${(volume * 100).round()}%', textAlign: TextAlign.end)),
+            ],
+          ),
+          Text('Soft cues for people and readiness; the video itself covers play, pause and the end. '
+              'Letting go of the slider plays the ready sound.', style: muted),
+          const SizedBox(height: 8),
+          for (final MapEntry(key: kind, value: (name, help)) in soundInfo.entries)
+            Padding(
+              padding: const EdgeInsets.symmetric(vertical: 2),
+              child: Row(
+                children: [
+                  IconButton(
+                    key: ValueKey('sound-play-${kind.name}'),
+                    tooltip: 'Play',
+                    onPressed: volume == 0 ? null : () => _preview(kind),
+                    icon: const Icon(Icons.play_arrow_rounded),
+                  ),
+                  const SizedBox(width: 4),
+                  Expanded(
+                    child: Column(
+                      crossAxisAlignment: CrossAxisAlignment.start,
+                      children: [Text(name), Text(help, style: muted)],
+                    ),
+                  ),
+                  Switch(
+                    key: ValueKey('sound-on-${kind.name}'),
+                    value: !off.contains(kind.name),
+                    onChanged: volume == 0 ? null : (on) => s.setSoundOn(kind.name, on),
+                  ),
+                ],
+              ),
+            ),
+        ],
+      );
+    });
+  }
+}