feat(01-03): create CLI entry point for testing

- Implement __main__.py with argparse command-line interface
- Add interactive chat loop for testing model switching
- Include status commands to show current model and resources
- Support models listing and manual model switching
- Add proper signal handling for graceful shutdown
- Include help text and usage examples
- Fix import issues for relative imports in package

src/models/model_manager.py

@@ -359,7 +359,7 @@ class ModelManager:
                     raise ValueError("Model returned empty or inadequate response")
 
                 # Add messages to context
-                from .conversation import MessageRole
+                from models.conversation import MessageRole
 
                 self.context_manager.add_message(
                     conversation_id, MessageRole.USER, message