Fix master volume not applied on startup

The mixer's start snapshot overwrites exposed params set before the
first frame, so the BeforeSceneLoad SetFloat was discarded. Re-apply
the saved volume after one frame (Awaitable.NextFrameAsync).

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

Assets/Scripts/Helper/MasterVolume.cs

@@ -72,11 +72,14 @@ public static class MasterVolume
             Debug.LogWarning($"[MasterVolume] Exposed parameter '{ExposedParam}' not found on the AudioMixer.");
     }
 
-    // Push the saved level before any scene audio starts. SetFloat overrides the exposed parameter
-    // permanently (until ClearFloat), so the start snapshot's authored value is superseded.
+    // Push the saved level at startup. SetFloat before the first frame is discarded when the mixer
+    // activates its start snapshot (known Unity behavior: exposed params set in Awake/BeforeSceneLoad
+    // get reset), so apply immediately for best effort and again one frame later to make it stick.
     [RuntimeInitializeOnLoadMethod(RuntimeInitializeLoadType.BeforeSceneLoad)]
-    private static void ApplyOnStartup()
+    private static async void ApplyOnStartup()
     {
         Apply(Volume);
+        await Awaitable.NextFrameAsync();
+        Apply(Volume);
     }
 }