Extract the Subagents array type from a DeepAgent.
InferDeepAgentSubagents: ExtractDeepAgentConfig<T> extends never never : ExtractDeepAgentConfig<T>["Subagents"]const agent = createDeepAgent({ subagents: [researcher, writer] as const });
type Subagents = InferDeepAgentSubagents<typeof agent>;
// Subagents is the readonly tuple of subagent definitions