[router] router circuit breaker core (#8941)

sgl-router/tests/streaming_tests.rs

@@ -4,7 +4,9 @@ use common::mock_worker::{HealthStatus, MockWorker, MockWorkerConfig, WorkerType
 use futures_util::StreamExt;
 use reqwest::Client;
 use serde_json::json;
-use sglang_router_rs::config::{PolicyConfig, RetryConfig, RouterConfig, RoutingMode};
+use sglang_router_rs::config::{
+    CircuitBreakerConfig, PolicyConfig, RetryConfig, RouterConfig, RoutingMode,
+};
 use sglang_router_rs::routers::{RouterFactory, RouterTrait};
 use std::sync::Arc;
 
@@ -37,6 +39,7 @@ impl TestContext {
             max_concurrent_requests: 64,
             cors_allowed_origins: vec![],
             retry: RetryConfig::default(),
+            circuit_breaker: CircuitBreakerConfig::default(),
         };
 
         let mut workers = Vec::new();