[sgl-router] refactor - move policy-required states under src/state (#40272)

Co-authored-by: Claude Fable 5.1 <noreply@anthropic.com>

experimental/sgl-router/tests/component/workers/concurrent_state.rs

@@ -131,17 +131,17 @@ fn load_guard_decrements_on_panic_unwind() {
         model_ids: vec![ModelId("m".into())],
         bootstrap_port: None,
     }));
-    assert_eq!(w.active_load(), 0);
+    assert_eq!(w.router_inflight_load(), 0);
 
     let w_inner = w.clone();
     let result = std::panic::catch_unwind(std::panic::AssertUnwindSafe(move || {
         let _g = w_inner.load_guard();
-        assert_eq!(w_inner.active_load(), 1);
+        assert_eq!(w_inner.router_inflight_load(), 1);
         panic!("synthetic panic to exercise Drop on unwind");
     }));
     assert!(result.is_err(), "the closure must have panicked");
     assert_eq!(
-        w.active_load(),
+        w.router_inflight_load(),
         0,
         "LoadGuard's Drop must decrement even when the holder panics",
     );

experimental/sgl-router/tests/component/workers/manager.rs

@@ -740,7 +740,7 @@ async fn removed_awaits_pending_added() {
 /// independently — 2N round-trips for N workers.
 #[tokio::test]
 async fn manager_emits_single_server_info_fetch_per_worker() {
-    use sgl_router::policies::kv_events::KvEventIndex;
+    use sgl_router::state::kv_events::KvEventIndex;
 
     let body = json!({
         "served_model_name": "m",