feat: add native runtime settings

src/MBN_STOCK_WEBVIEW.Playout/Configuration/PlayoutOptionsLoader.cs

@@ -19,14 +19,43 @@ public static class PlayoutOptionsLoader
         "Config",
         "playout.local.json");
 
-    public static PlayoutOptions Load(string? path = null)
+    public static PlayoutOptions Load(
+        string? path = null,
+        string? operatorSceneDirectory = null,
+        string? operatorBackgroundDirectory = null)
     {
         var options = LoadJson(path ?? DefaultPath);
+        ApplyOperatorAssetOverrides(
+            options,
+            operatorSceneDirectory,
+            operatorBackgroundDirectory);
         ApplyEnvironment(options);
         ApplyExecutableAssetDefaults(options, AppContext.BaseDirectory);
         return options;
     }
 
+    /// <summary>
+    /// Applies only the two non-command asset roots selected by the native settings
+    /// screen. Process environment values are applied afterwards and therefore retain
+    /// precedence for controlled diagnostic and development-live launches.
+    /// </summary>
+    internal static void ApplyOperatorAssetOverrides(
+        PlayoutOptions options,
+        string? sceneDirectory,
+        string? backgroundDirectory)
+    {
+        ArgumentNullException.ThrowIfNull(options);
+        if (!string.IsNullOrWhiteSpace(sceneDirectory))
+        {
+            options.SceneDirectory = sceneDirectory.Trim();
+        }
+
+        if (!string.IsNullOrWhiteSpace(backgroundDirectory))
+        {
+            options.LegacyBackgroundDirectory = backgroundDirectory.Trim();
+        }
+    }
+
     /// <summary>
     /// Loads only the specified JSON file and deliberately ignores all environment
     /// overrides. Intended for explicit, reproducible diagnostic commands.