[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/discovery/static_urls.rs

@@ -90,8 +90,7 @@ async fn static_urls_pd_role_resolved_end_to_end() {
     use axum::{routing::get, Json, Router};
     use serde_json::json;
     use sgl_router::config::{
-        ActiveLoadConfig, Config, DiscoveryBackend, DiscoveryConfig, ObservabilityConfig,
-        ProxyConfig, ServerConfig,
+        ActiveLoadConfig, Config, DiscoveryBackend, ObservabilityConfig, ProxyConfig, ServerConfig,
     };
     use sgl_router::discovery::{spawn_discovery, WorkerId};
     use sgl_router::workers::{manager, WorkerRegistry};
@@ -127,12 +126,16 @@ async fn static_urls_pd_role_resolved_end_to_end() {
             port: 0,
         },
         observability: ObservabilityConfig::default(),
-        models: vec![],
-        discovery: DiscoveryConfig {
-            backend: DiscoveryBackend::StaticUrls(StaticUrlsDiscoveryConfig {
-                urls: vec![url.clone()],
-            }),
+        model: sgl_router::config::ModelConfig {
+            id: "tiny".into(),
+            tokenizer_path: "tests/fixtures/tiny_tokenizer.json".into(),
+            policy: sgl_router::config::PolicyKind::RoundRobin,
+            circuit_breaker: None,
+            cache_aware: None,
         },
+        discovery: DiscoveryBackend::StaticUrls(StaticUrlsDiscoveryConfig {
+            urls: vec![url.clone()],
+        }),
         proxy: ProxyConfig::default(),
         active_load: ActiveLoadConfig::default(),
     };