Fix router keep nonzero metrics after worker is deleted (#14819)

sgl-model-gateway/src/core/worker_registry.rs

@@ -8,6 +8,7 @@ use dashmap::DashMap;
 use uuid::Uuid;
 
 use crate::core::{ConnectionMode, RuntimeType, Worker, WorkerType};
+use crate::observability::metrics::RouterMetrics;
 
 /// Unique identifier for a worker
 #[derive(Debug, Clone, Hash, Eq, PartialEq)]
@@ -138,8 +139,8 @@ impl WorkerRegistry {
                 conn_workers.retain(|id| id != worker_id);
             }
 
-            // TODO we may even remove it from Prometheus exports
             worker.set_healthy(false);
+            RouterMetrics::remove_worker_metrics(worker.url());
 
             Some(worker)
         } else {