0361 — MessageProducer.Register(ctx) captures the instance lifetime and gates Produce

Context. Producers had no lifetime at all — no ctx, no Run, no Close — while the presence/heartbeat design needs a lifetime goroutine per producer, and graceful shutdown needs an owner for “accept nothing new, drain what you hold”. A per-call ctx cannot carry instance truth: HTTP request ctxs survive SIGTERM, and background jobs pass context.Background().

Decision. MessageProducer.Register(ctx) mirrors the consumer’s lifecycle: the ctx scopes the instance, stored as lifecycleCtx. One gate helper (lifecycleErr) guards Produce/ProduceFunc/ProduceInTx: not registered returns ErrNotRegistered, cancelled returns ErrShutdownRequested. Wind-down means drain: the batcher worker stays deliberately ctx-blind, so queued work commits and the worker exits when the queue empties, with zero new batcher code.

Consequences. Wind-down attempts succeed — the opposite of the circuit breaker’s stop-the-buffer posture, where breaker-open means attempts fail. Superseded 2026-08-08: producer lifecycle capture was dropped by the user — Register(ctx, topic, version) became stateless, shutdown is observed per produce call, and ErrShutdownRequested plus the producer’s DisableGracefulShutdown were deleted.