fix: assign UniverseWrapper in UniverseSetupScreen.setEnvironment

setEnvironment() received a UniverseWrapper parameter but never assigned it
to the instance field. The screen's UI bindings read from the field, not the
context, so seed/generator/server settings from AdvancedGameSetupScreen were
silently discarded.

Flagged independently by both Copilot and CodeRabbit on PR #5299.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

engine/src/main/java/org/terasology/engine/rendering/nui/layers/mainMenu/UniverseSetupScreen.java

@@ -383,6 +383,7 @@ private void addNewWorld(WorldGeneratorInfo worldGeneratorInfo) {
      * needed for successful game creation.
      */
     public void setEnvironment(UniverseWrapper universeWrapper) {
+        this.universeWrapper = universeWrapper;
         prepareContext();
 
         DependencyResolver resolver = new DependencyResolver(moduleManager.getRegistry());