Whether to auto-add the default general-purpose subagent (three-state:
None inherits / defaults on, True forces inclusion, False disables).
None means inherit from a base profile when merging, or fall back to
the default of including the subagent. True forces inclusion and is
what a model-level profile can use to re-enable a subagent that a
provider-level profile disabled. False disables the auto-added
subagent entirely.
If the default subagent is disabled and no other synchronous subagents are
configured, the main agent will not expose the task tool.
