validateModel method
Validates if a model is properly installed
Phase 5.3: Delegates to Modern API (isModelInstalled) instead of checking manual _installedModels map.
Implementation
@override
Future<bool> validateModel(ModelSpec spec) async {
await _ensureInitialized();
// Phase 5: Delegate to Modern API
// validateModel is essentially the same as isModelInstalled on web
return await isModelInstalled(spec);
}