transformOutcome
open suspend override fun <S> transformOutcome(output: Result<O>, channel: SerializedService<S>, encodeError: (Throwable) -> CallData.Error<S>): CallData<S>
Server-side boundary hook (issue #133). Invoked by RpcMethod.call with the value returned by the handler. The default implementation simply delegates to transform; transformers that need to observe the failure channel (e.g. ResultTransformer for Result<O> return types) override this to fold a returned failure into the wire-level error frame via encodeError.
Implementations MUST rethrow CancellationException to preserve structured concurrency.