[router] fix: validate HTTP status codes in health check (#12631)

Author: wyx-0203

sgl-router/src/core/workflow/steps/worker_registration.rs

@@ -145,6 +145,7 @@ async fn try_http_health_check(
         .timeout(Duration::from_secs(timeout_secs))
         .send()
         .await
+        .and_then(reqwest::Response::error_for_status)
         .map_err(|e| format!("Health check failed: {}", e))?;
 
     Ok(())