Function link_with_deferred_resolution 

pub async fn link_with_deferred_resolution(
    program: Program,
    host_environment: LashlangHostEnvironment,
    resolver: Option<&SharedDeferredToolResolver>,
    record: &mut DeferredResolutionRecord,
) -> Result<LinkedModule, LinkError>

gather → resolve → link: resolve_and_fold_deferred then link. Used by callers that do not maintain their own compile cache. NotAvailable (and no resolver) leaves the symbol unresolved, surfacing a clean model-visible link error.