general_purpose_subagent: GeneralPurposeSubagentProfile | None = NoneEdits 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.