feat(acp-nats): add client proxy for session.update notifications

Subscribes to the client NATS subject namespace and forwards
SessionUpdate notifications to the ACP client. Includes backpressure
limiting, subject validation, in-flight slot tracking, and session ID
mismatch detection.

Signed-off-by: Yordis Prieto <yordis.prieto@gmail.com>

Author: yordis

rsworkspace/Cargo.lock

@@ -8,9 +8,11 @@ workspace = true
 
 [dependencies]
 agent-client-protocol = "0.9.4"
-opentelemetry = "0.31.0"
 async-nats = "0.45.0"
 async-trait = "0.1.89"
+bytes = "1.9"
+futures = "0.3"
+opentelemetry = "0.31.0"
 serde = { version = "1.0.228", features = ["derive"] }
 serde_json = "1.0.149"
 tokio = { version = "1.49.0", features = ["rt", "macros", "sync", "time"] }