Function parse_delegate_args 

pub fn parse_delegate_args(
    call_id: &str,
    args_json: &str,
) -> Option<DelegateRequest>

Parse the JSON arguments of a __delegate_to tool call into a structured DelegateRequest.

Returns None if args_json doesn’t parse, or either required field (target_agent_id, task) is missing or empty — the caller then surfaces a legible tool-result error rather than dispatching a malformed delegation.