Making plans visible

The TodoWrite tool lets the model create and update a structured task list. Each item has a subject, description, status (pending/in_progress/completed), and an activeForm for the UI spinner. The list is injected before every LLM call as a system reminder.

The nag reminder is a simple but powerful pattern. Before each LLM call, if the TodoManager has items, a compact summary is injected into the conversation. This keeps the plan visible without the model having to remember it. The model sees its own plan every single turn.