[router] Configure experimental sgl-router via CLI flags instead of a config file (#27073)

Signed-off-by: Kangyan Zhou <zky314343421@gmail.com>
Co-authored-by: Claude Opus 4.8 <noreply@anthropic.com>

experimental/sgl-router/tests/component/policies/kv_events_two_subscribers.rs

@@ -41,6 +41,7 @@ async fn two_independent_subscribers_converge_to_same_tree_state() {
         topic: String::new(),
         block_size,
         dp_size: 1,
+        is_bigram: false,
     };
 
     // 2. Two independent router-process surrogates, each with its own
@@ -173,6 +174,7 @@ async fn two_subscribers_merge_events_from_two_publishers() {
         topic: String::new(),
         block_size,
         dp_size: 1,
+        is_bigram: false,
     };
     let cfg_y = EventConfig {
         host: "127.0.0.1".into(),
@@ -180,6 +182,7 @@ async fn two_subscribers_merge_events_from_two_publishers() {
         topic: String::new(),
         block_size,
         dp_size: 1,
+        is_bigram: false,
     };
 
     // Both routers subscribe to BOTH workers — the production fan-out.