Optional Legion 0.6.0 execution in isolated Lua agents.
Supply :execution, a request factory returning %{model: model_spec, task: string, operations: %{name => zero_arity_function}, result: mapper}.
Tools call only these operations; their native results, not model claims,
reach the mapper. All supplied operations must succeed before Tool.complete().
The model spec supports ReqLLM's {provider, model, options} form, allowing
transport options and controlled model fixtures. The host configures ReqLLM's
provider credentials separately; api_key is not accepted in tuple defaults.
Persistence, recovery, delegation and conversation sharing are unsupported. Cancellation stops local work and leaves external outcomes uncertain.