fix: update callers to use NewLLMRouterDefault

Use NewLLMRouterDefault(kb) instead of NewLLMRouter(kb) in:
- action/router.go
- cmd/starter/main.go

The NewLLMRouter now requires LLMRouterConfig{} struct.
Backward compat wrapper NewLLMRouterDefault() maintains old API.

action/router.go

@@ -19,8 +19,8 @@ func LLMRouterActivity(ctx context.Context, input routing.LLMRouterInput) (*rout
 		return nil, fmt.Errorf("failed to load knowledge base: %w", err)
 	}
 
-	// Create router
-	router, err := routing.NewLLMRouter(kb)
+	// Create router with default LLM provider
+	router, err := routing.NewLLMRouterDefault(kb)
 	if err != nil {
 		return nil, fmt.Errorf("failed to create router: %w", err)
 	}