feat(ui): add bundled custom notification sounds

Adds three embedded WAV files as additional notification sound choices
(ids 17-19) alongside the existing 16 game sounds. Playback via NAudio
WaveOutEvent/WinMM, which works correctly on Wine/Linux.

HellionChat/MessageManager.cs

@@ -363,16 +363,26 @@ internal class MessageManager : IAsyncDisposable
 
         if (notificationSound is { } soundId)
         {
-            // ProcessMessage runs on the PendingMessageThread worker; the native
-            // UIGlobals.PlaySoundEffect must be marshalled onto the framework
-            // thread (reference_dalamud_framework_thread).
-            Plugin.Framework.RunOnFrameworkThread(() =>
+            if (soundId is >= 1 and <= 16)
             {
-                unsafe
+                // ProcessMessage runs on the PendingMessageThread worker; the native
+                // UIGlobals.PlaySoundEffect must be marshalled onto the framework
+                // thread (reference_dalamud_framework_thread).
+                Plugin.Framework.RunOnFrameworkThread(() =>
                 {
-                    UIGlobals.PlaySoundEffect(soundId);
-                }
-            });
+                    unsafe
+                    {
+                        UIGlobals.PlaySoundEffect(soundId);
+                    }
+                });
+            }
+            else if (soundId >= 17)
+            {
+                // Custom bundled sounds (ids 17-19) go through NAudio WaveOutEvent.
+                // NAudio manages its own playback thread, so no framework marshalling needed.
+                Plugin.CustomAudioPlayer.Play((int)soundId - 16);
+            }
+            // soundId == 0 (hand-edited config) falls through: plays nothing.
         }
 
         MessageProcessed?.Invoke(message);