### Summary Sometimes in exec runs, we want to allow the model to use the `update_plan` tool, but that's not easily configurable. This change adds a feature flag for this, and formats the output so it's human-readable ## Test Plan <img width="1280" height="354" alt="Screenshot 2025-09-11 at 12 39 44 AM" src="https://github.com/user-attachments/assets/72e11070-fb98-47f5-a784-5123ca7333d9" />