delegate_task has never exposed a per-call model parameter (removed
intentionally in fb0f579b1). The tool description gave no hint about how
subagent model is actually controlled, so users kept expecting a model
arg and filing it as a dropped/ignored param (e.g. #49332, #23467).
Add one bullet to the dynamically-built tool description stating that
children inherit the parent model + fallback chain, and that pinning all
subagents to a specific model is done via delegation.provider /
delegation.model in config.yaml. No behavior change.
a6f08ff0c8