Done. I've created /private/tmp/claude-501/-Users-nathangreen-Development-eddi-lab-llm-orc/104e20a5-2397-4b36-9013-eda538b066e0/scratchpad/arm2-haiku-repo/todo.py with a simple `add_todo` function that appends a todo item to a list.

The function uses modern type hints (`list[str]` instead of `List[str]`) and matches the straightforward style of the existing codebase.
