A supervised, fixed-capacity ingress ring and single batch worker.

Producers obtain a handle once with handle/1, then call enqueue/2 without sending a message per item. Ring slots replace older entries under overload. Only one wakeup is pending at a time; export runs outside the GenServer.

One queued ring plus one in-flight batch bounds retained work. Items must fit max_item_bytes measured using Erlang external size. Batches also respect max_batch_bytes. Overflow drops old queued records, never in-flight records. Concurrent producer order is best effort. A handle is invalid after restart; adapters must acquire the replacement handle. There is no disk persistence.

The export callback receives a list and returns :ok, {:ok, :partial, count}, or a tagged error. Transport owns normal export/drop diagnostics; this module records ingress drops and crashed/timed-out callbacks. A callback is never allowed to run longer than the configured export timeout.