feat: implement CreateGrant handler and grant-aware approval engine

- GlobalStreamHandler.handleCreateGrant validates scope (SESSION/STAGE)
  and sends ProtocolError to client on validation failure instead of
  silent log.warn + drop.
- Derive event stageId directly from GrantScope type, removing
  redundant stageIdForEvent tuple.
- SessionOrchestrator integrates ApprovalEngine to check active grants
  before requesting user approval for T2+ tool calls.
- ContextEntry gains EntryRole (SYSTEM/USER/ASSISTANT/TOOL) field for
  proper chat message role mapping.
- RouterContextBuilder.build is now suspend; uses Tokenizer for
  accurate token estimation with fallback to character-based estimate.
- LlamaCppInferenceProvider maps EntryRole to ChatMessage role instead
  of heuristic layer-based inference.

infrastructure/src/main/kotlin/com/correx/infrastructure/InfrastructureModule.kt

@@ -10,6 +10,7 @@ import com.correx.core.events.EventDispatcher
 import com.correx.core.events.stores.EventStore
 import com.correx.core.inference.InferenceProvider
 import com.correx.core.inference.InferenceRouter
+import com.correx.core.inference.Tokenizer
 import com.correx.core.router.DefaultRouterContextBuilder
 import com.correx.core.router.DefaultRouterFacade
 import com.correx.core.router.DefaultRouterReducer
@@ -120,12 +121,13 @@ object InfrastructureModule {
         eventStore: EventStore,
         inferenceRouter: InferenceRouter,
         config: RouterConfig = RouterConfig(),
+        tokenizer: Tokenizer? = null,
     ): RouterFacade {
         val reducer = DefaultRouterReducer()
         val projector = RouterProjector(reducer)
         val replayer = DefaultEventReplayer(eventStore, projector)
         val repository = DefaultRouterRepository(replayer)
-        val contextBuilder = DefaultRouterContextBuilder(config)
+        val contextBuilder = DefaultRouterContextBuilder(config, tokenizer)
         return DefaultRouterFacade(repository, contextBuilder, inferenceRouter, eventStore, config)
     }
 }