* fix: update default LLM model and improve error logging in LLM utilities
* Updated the default LLM model from "gpt-4o-mini" to "gpt-4.1-mini" for better performance.
* Enhanced error logging in the LLM utilities to use logger.error instead of logger.debug, ensuring that errors are properly reported and raised.
* Added tests to verify behavior when OpenAI API key is missing and when Anthropic dependency is not available, improving robustness and error handling in LLM creation.
* fix: update test for default LLM model usage
* Refactored the test_create_llm_with_none_uses_default_model to use the imported DEFAULT_LLM_MODEL constant instead of a hardcoded string.
* Ensured that the test correctly asserts the model used is the current default, improving maintainability and consistency across tests.
* change default model to gpt-4.1-mini
* change default model use defualt