Function prefetch_external_resources 

pub async fn prefetch_external_resources(
    bundle: &SofBundle,
    config: &RemoteResolveConfig,
) -> Vec<FhirResource>

Fetches the allowlisted external references reachable from bundle and returns them as parsed resources to merge into the resolution pool (single-Bundle path).

Returns an empty vector when remote resolution is inactive. Never errors: every failure mode (disallowed host, timeout, non-2xx, oversize, unparseable) is logged and skipped, leaving the reference to fall back to the in-scope typed-stub/empty behaviour.