Enable CodeInterpreterMiddleware (js_eval REPL) on the main agent.
Always the resolved concrete value: from_cli_args collapses the tri-state
caller option via _resolve_enable_interpreter before constructing the
config, so the bool | None "defer to default" sentinel never reaches this
field. The False default here is only the bare-constructor/from_env
fallback; the user-facing default (on in local mode) lives in
settings.enable_interpreter.
Local-mode only; the server graph raises if a sandbox is configured and
this flag is True.
