feat: make LegacyParityApp playout live-only

src/MBN_STOCK_WEBVIEW.LegacyParityApp/MainWindow.Playout.cs

@@ -32,21 +32,33 @@ public sealed partial class MainWindow
     {
         try
         {
+            if (_developmentLiveStartupBlocked)
+            {
+                _playoutInitializationError =
+                    App.DevelopmentLiveStartupFailureMessage ??
+                    "Live playout startup validation failed.";
+                return;
+            }
+
             var explicitLocalConfigurationExists = File.Exists(
                 PlayoutOptionsLoader.DefaultPath);
             _playoutOptions =
-                _isDevelopmentLiveLaunch &&
-                !_developmentLiveStartupBlocked
+                _isDevelopmentLiveLaunch
                 ? PlayoutOptionsLoader.LoadDevelopmentLive(
                     baseDirectory: AppContext.BaseDirectory,
                     operatorSceneDirectory:
                         _appliedOperatorSettings.SceneDirectory)
                 : PlayoutOptionsLoader.Load(
                     operatorSceneDirectory: _appliedOperatorSettings.SceneDirectory,
-                    operatorBackgroundDirectory: _appliedOperatorSettings.BackgroundDirectory,
-                    forceSafeDryRun: IsSourceOnlyBuild ||
-                        _isDevelopmentLiveLaunchRequested ||
-                        _developmentLiveStartupBlocked);
+                    operatorBackgroundDirectory:
+                        _appliedOperatorSettings.BackgroundDirectory);
+            if (_playoutOptions.Mode != PlayoutMode.Live)
+            {
+                throw new PlayoutConfigurationException(
+                    "The application requires a validated Live playout configuration. " +
+                    "DryRun fallback is disabled.");
+            }
+
             ResetRefreshState();
             var startupComposition = LegacyParityStartupCompositionResolver.Resolve(
                 _playoutOptions,
@@ -75,6 +87,7 @@ public sealed partial class MainWindow
         }
         catch (Exception exception)
         {
+            _developmentLiveStartupBlocked = true;
             _playoutInitializationWarning = null;
             _playoutInitializationError = exception is PlayoutConfigurationException
                 ? exception.Message