[router] Tokenize prompt once at ingress; forward input_ids to the engine (all policies) (#28744)

Co-authored-by: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

experimental/sgl-router/tests/proxy/main.rs

@@ -10,11 +10,14 @@
 
 mod common;
 
+mod cache_aware_input_ids;
 mod chat_routing;
 mod failover;
 mod graceful_shutdown;
 mod header_forwarding;
 mod pd_bootstrap_injection;
 mod pd_pool_isolation;
+mod roundrobin_input_ids;
+mod sticky_input_ids;
 mod sticky_routing;
 mod timeout;