general_purpose_subagent

Edits for the auto-added general-purpose subagent.

Unset (default None) is equivalent to passing GeneralPurposeSubagentProfile() — the auto-added subagent runs with its stock description and prompt. Set enabled=False on a populated sub-profile to remove the default general-purpose subagent entirely. Pair that with no synchronous subagents via subagents= on create_deep_agent and the task tool is dropped too. Async subagents are unaffected.