fix: clear gameObjectDisplayIdWmoCache_ on world transition, add stale-entry guard

gameObjectDisplayIdWmoCache_ was not cleared on world unload/transition,
causing stale WMO model IDs (e.g. 40006, 40003) to be looked up after
the renderer cleared its model list, resulting in "Cannot create instance
of unloaded WMO model" errors on zone re-entry.

Changes:
- Clear gameObjectDisplayIdWmoCache_ alongside other GO caches on world reset
- Add WMORenderer::isModelLoaded() for cache-hit validation
- Inline GO WMO path now verifies cached model is still renderer-resident
  before using it; evicts stale entries and falls back to reload

src/core/application.cpp

@@ -4113,6 +4113,7 @@ void Application::loadOnlineWorldTerrain(uint32_t mapId, float x, float y, float
 
         gameObjectInstances_.clear();
         gameObjectDisplayIdModelCache_.clear();
+        gameObjectDisplayIdWmoCache_.clear();
         gameObjectDisplayIdFailedCache_.clear();
 
         // Force player character re-spawn on new map
@@ -7115,8 +7116,15 @@ void Application::spawnOnlineGameObject(uint64_t guid, uint32_t entry, uint32_t
         auto itCache = gameObjectDisplayIdWmoCache_.find(displayId);
         if (itCache != gameObjectDisplayIdWmoCache_.end()) {
             modelId = itCache->second;
-            loadedAsWmo = true;
-        } else {
+            // Only use cached entry if the model is still resident in the renderer
+            if (wmoRenderer->isModelLoaded(modelId)) {
+                loadedAsWmo = true;
+            } else {
+                gameObjectDisplayIdWmoCache_.erase(itCache);
+                modelId = 0;
+            }
+        }
+        if (!loadedAsWmo && modelId == 0) {
             auto wmoData = assetManager->readFile(modelPath);
             if (!wmoData.empty()) {
                 pipeline::WMOModel wmoModel = pipeline::WMOLoader::load(wmoData);