refactor(workspace): restore yaml exports and align docker builds

- return scenario export payloads as yaml to match existing workflows

- harden step reordering flow for drag-and-drop and one-based ui labels

- switch server container to workspace-lockfile installs and root ignore rules

client/src/api/client.ts

@@ -27,9 +27,13 @@ async function request<T>(path: string, init?: RequestInit): Promise<T> {
   }
   const contentLength = res.headers.get('content-length');
   if (res.status === 204 || contentLength === '0') return undefined as T;
+  const contentType = res.headers.get('content-type')?.toLowerCase() ?? '';
   const text = await res.text();
   if (!text) return undefined as T;
-  return JSON.parse(text) as T;
+  if (contentType.includes('application/json')) {
+    return JSON.parse(text) as T;
+  }
+  return text as T;
 }
 
 // ── Credentials ───────────────────────────────────────────────────────────────
@@ -185,7 +189,7 @@ export const scenarios = {
   ): Promise<PaginatedResponse<ScenarioRun & { stepRuns: ScenarioRunStep[] }>> {
     return request(`/scenarios/${scenarioId}/runs?page=${page}&limit=${limit}`);
   },
-  exportScenario(id: string): Promise<unknown> {
+  exportScenario(id: string): Promise<string> {
     return request(`/scenarios/${id}/export`);
   },
   importScenario(payload: unknown): Promise<Scenario> {
@@ -247,7 +251,6 @@ export const scenarioCredentials = {
 // ── Scenario Steps ────────────────────────────────────────────────────────────
 export interface CreateStepPayload {
   title?: string;
-  order: number;
   execCode?: string;
   validateCode?: string;
 }