23543b2ba8
JetStream async file publish optimization (~10% improvement): - Cached state properties eliminate GetStateAsync on publish path - Single stream lookup eliminates double FindBySubject - Removed _messageIndexes dictionary from write path - Hand-rolled UTF-8 pub-ack formatter for success path - Exponential flush backoff matching Go server - Lazy StoredMessage materialization (MessageMeta struct) # Conflicts: # benchmarks_comparison.md