Configure routing on a newly-inserted Enhanced `MessagingChannel` so activation will accept it. Given a `{CHANNEL_ID}`, walks through picking a routing type (Omni-Channel Queue, Omni-Flow, Agentforce Service Agent, Digital Worker, or direct User), locates or provisions the target, then PATCHes `SessionHandlerId` (plus `FallbackQueueId` where required). Use between insertion and activation — activation fails server-side with `nullQueueId`/`LiveMessageSetupException` if no valid `SessionHandlerId` is set. Do not use for full end-to-end setup — use `service-de-headless-channel-configure`.
