Pulsar: tiered retry-letter error policy MoveToPulsarRetryTopic (#3182)

[jeremydmiller]

Closes #3182. Part of the Re-Evaluate Pulsar Integration epic #3176.

Adds a first-class, discoverable retry-letter error policy — the Pulsar analogue of MoveToKafkaRetryTopic:

opts.ListenToPulsarTopic("persistent://public/default/orders")
    .SubscriptionType(SubscriptionType.Shared);

opts.OnException<TransientException>()
    .MoveToPulsarRetryTopic(5.Seconds(), 30.Seconds(), 2.Minutes());

Each TimeSpan is one retry tier: on failure the message is routed through Pulsar's native retry-letter topic with that delay, reprocessed by the retry consumer once it elapses, and after the last tier is exhausted it lands in the dead-letter topic.

How it works

• MoveToPulsarRetryTopicContinuation (a UserDefinedContinuation, not an opaque CustomAction) self-guards to PulsarListener — a failure arriving over any other transport falls back to a normal inline retry, never cross-transport — and is discoverable in diagnostics.
• PulsarTransport discovers the policy at startup and wires its per-tier delays onto every Pulsar listener (provisioning the retry-letter producer/consumer + DLQ), so an explicit RetryLetterQueueing(...) is not also required.
• Startup validation warnings when (a) non-Pulsar listeners are present (policy degrades to inline retry there), or (b) a Pulsar listener uses a subscription type other than Shared/Key_Shared (Pulsar message delaying does not work there).

Acceptance criteria

• ✅ The DSL routes a failed message through tiered retry-letter delays then to DLQ — integration test (permanent_failure_walks_the_tiers_then_dead_letters: 3 deliveries → 1 dead-lettered).
• ✅ Applying it to a non-Pulsar listener emits a startup warning — integration test (non_pulsar_listener_emits_a_startup_warning).
• ✅ Docs section added for Key_Shared by-key concurrency (the free Pulsar analogue of Kafka Kafka: opt-in intra-partition concurrency by key (durable, reuse ShardedExecutionBlock) #3140).

Tests / build

• pulsar_retry_topic_dsl: 2/2 green against a Testcontainers broker.
• Full wolverine.slnx builds clean in Release.

🤖 Generated with Claude Code