Update app.py to use correct retriever config for HF deployment

- Changed default config from compute_rag_vector_index_conversations.yaml to compute_rag_vector_index_openai_contextual.yaml
- This ensures HF Space uses the optimized contextual retriever with all improvements

app.py

@@ -28,7 +28,7 @@ except ImportError as e:
 def main():
     """Main function for Hugging Face Space deployment."""
     # Set default values for HF Spaces
-    retriever_config_path = os.getenv("RETRIEVER_CONFIG_PATH", "configs/compute_rag_vector_index_conversations.yaml")
+    retriever_config_path = os.getenv("RETRIEVER_CONFIG_PATH", "configs/compute_rag_vector_index_openai_contextual.yaml")
     
     print("🚀 Starting Second Brain AI Assistant...")
     print(f"📁 Using retriever config: {retriever_config_path}")