修复跨设备画布旧快照覆盖

按用户隔离画布缓存并等待权威 revision 后开放保存
固化保存重试版本并安全处理认证重载与冲突恢复
合并迟到资源图层且隔离跨账号异步请求
强制 Web 与 External 画布写入使用 expectedRevision CAS
补充竞态回归测试并同步 OpenAPI、Skill 与技术文档

src/services/image-editor/editorProjectClient.ts

@@ -555,13 +555,13 @@ export type EditorProjectCreateInput = {
 export type EditorProjectLayoutSaveInput = {
   viewport: EditorCanvasViewport;
   layers: EditorProjectLayerSnapshot[];
-  expectedRevision?: number;
+  expectedRevision: number;
 };
 
 export type EditorProjectLayoutSaveResult = {
   projectId: string;
   canvasId: string;
-  revision?: number;
+  revision: number;
   updatedAt: string;
 };