Extracts the content of a user's message from an LLMMessage object at a specific index.
get_user_message(.llm, .index = NULL)
last_user_message(.llm)Returns the content of the user's message at the specified index. If no messages are found, returns NA_character_.
For convenience, last_user_message() is provided as a wrapper to retrieve the
latest user message without specifying an index.
last_user_message()