Add NATS JetStream and Kafka EventStore providers

[Raezil]

Implements the first priority slice of #22.

Added

• WithNATSJetStream(...) / NATSJetStreamProvider
  • EventStore-first lazy construction
  • projection → subject mapping
  • durable consumers
  • queue groups
  • explicit ACK after successful handling
  • NAK on decode/handler failure
  • custom EventCodec
  • graceful provider shutdown without closing the injected NATS connection
• WithKafka(...) / KafkaProvider
  • EventStore-first lazy construction
  • topic publishing
  • consumer groups
  • optional fixed partition mode
  • projection-keyed hashing for partition-aware ordering
  • synchronous offset commit only after successful handling
  • custom EventCodec
  • graceful reader/writer shutdown
• configuration and projection-validation tests
• README examples and delivery/ownership semantics

This intentionally lands the issue's two priority transports first rather than ten broker clients in one unreviewable patch. Remaining providers in #22 can reuse the same EventStoreOption model.

Local go test could not be run in this execution environment because outbound module/GitHub DNS is blocked; CI is the compile/test gate.

Part of #22.

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Project	Deployment	Actions	Updated
goeventbus	Ready	Preview	Oct 5, 2026 5:51pm UTC