[router] regular router circuit breaker (#8997)

sgl-router/src/core/mod.rs

@@ -8,6 +8,7 @@
 
 pub mod circuit_breaker;
 pub mod error;
+pub mod retry;
 pub mod worker;
 
 // Re-export commonly used types at the module level
@@ -15,6 +16,7 @@ pub use circuit_breaker::{
     CircuitBreaker, CircuitBreakerConfig, CircuitBreakerStats, CircuitState,
 };
 pub use error::{WorkerError, WorkerResult};
+pub use retry::{BackoffCalculator, RetryError, RetryExecutor};
 pub use worker::{
     start_health_checker, BasicWorker, DPAwareWorker, HealthChecker, Worker, WorkerCollection,
     WorkerFactory, WorkerLoadGuard, WorkerType,