[model-gateway] refactor: extract workflow engine to src/workflow module (#14996)

sgl-model-gateway/tests/wasm_test.rs

@@ -18,9 +18,7 @@ use axum::{
 use sgl_model_gateway::{
     app_context::AppContext,
     config::RouterConfig,
-    core::workflow::{
-        create_wasm_module_registration_workflow, create_wasm_module_removal_workflow,
-    },
+    core::steps::{create_wasm_module_registration_workflow, create_wasm_module_removal_workflow},
     routers::RouterFactory,
     server::{build_app, AppState},
     wasm::{
@@ -113,8 +111,9 @@ async fn create_test_context_with_wasm() -> Arc<AppContext> {
         .expect("JobQueue should only be initialized once");
 
     // Initialize WorkflowEngine and register workflows
-    use sgl_model_gateway::core::workflow::{
-        create_worker_registration_workflow, create_worker_removal_workflow, WorkflowEngine,
+    use sgl_model_gateway::{
+        core::steps::{create_worker_registration_workflow, create_worker_removal_workflow},
+        workflow::WorkflowEngine,
     };
     let engine = Arc::new(WorkflowEngine::new());
     engine.register_workflow(create_worker_registration_workflow(&config));
@@ -684,8 +683,9 @@ async fn test_wasm_module_execution() {
         .expect("Workflow engine should be initialized");
 
     // Create workflow context for registration
-    use sgl_model_gateway::core::workflow::{
-        steps::WasmModuleConfigRequest, WorkflowContext, WorkflowId, WorkflowInstanceId,
+    use sgl_model_gateway::{
+        core::steps::WasmModuleConfigRequest,
+        workflow::{WorkflowContext, WorkflowId, WorkflowInstanceId},
     };
 
     let descriptor = WasmModuleDescriptor {
@@ -727,14 +727,14 @@ async fn test_wasm_module_execution() {
             .expect("Failed to get workflow status");
 
         match state.status {
-            sgl_model_gateway::core::workflow::WorkflowStatus::Completed => {
+            sgl_model_gateway::workflow::WorkflowStatus::Completed => {
                 // Extract module UUID from context
                 if let Some(uuid_arc) = state.context.get::<Uuid>("module_uuid") {
                     module_uuid = Some(*uuid_arc.as_ref());
                 }
                 break;
             }
-            sgl_model_gateway::core::workflow::WorkflowStatus::Failed => {
+            sgl_model_gateway::workflow::WorkflowStatus::Failed => {
                 panic!("Workflow failed: {:?}", state);
             }
             _ => {