feat(annotation): 添加标注对象解析和导出功能

- 实现 isAnnotationObject 函数验证标注对象
- 添加 resolveSelectedAnnotation 函数解析选中标注
- 优化 exportSelectedAnnotation 函数的标注选择逻辑
- 添加未找到标注对象的错误处理
- 支持 results 字段到 result 字段的自动转换
- 提升标注数据导出的稳定性和准确性

frontend/public/lsf/lsf.html

@@ -169,6 +169,33 @@
           }
         }
 
+        function isAnnotationObject(value) {
+          if (!value || typeof value !== "object") return false;
+          return typeof value.serializeAnnotation === "function" || typeof value.serialize === "function";
+        }
+
+        function resolveSelectedAnnotation(store) {
+          if (!store) return null;
+          const annotations = Array.isArray(store.annotations) ? store.annotations : [];
+          if (isAnnotationObject(store.selectedAnnotation)) {
+            return store.selectedAnnotation;
+          }
+          if (isAnnotationObject(store.selected)) {
+            return store.selected;
+          }
+          const selectedId = store.selected;
+          if (selectedId !== undefined && selectedId !== null && annotations.length) {
+            const matched = annotations.find((ann) => ann && String(ann.id) === String(selectedId));
+            if (isAnnotationObject(matched)) {
+              return matched;
+            }
+          }
+          if (annotations.length && isAnnotationObject(annotations[0])) {
+            return annotations[0];
+          }
+          return null;
+        }
+
         function exportSelectedAnnotation() {
           if (!lsInstance) {
             throw new Error("LabelStudio 未初始化");
@@ -179,10 +206,10 @@
             throw new Error("无法访问 annotationStore");
           }
 
-          const selected =
-            store.selected ||
-            store.selectedAnnotation ||
-            (Array.isArray(store.annotations) && store.annotations.length ? store.annotations[0] : null);
+          const selected = resolveSelectedAnnotation(store);
+          if (!selected) {
+            throw new Error("未找到可导出的标注对象");
+          }
 
           let serialized = null;
           if (selected && typeof selected.serializeAnnotation === "function") {
@@ -197,6 +224,10 @@
               ? { id: selected?.id || serialized.id || "draft", ...serialized }
               : { id: selected?.id || "draft", result: (selected && selected.result) || [] };
 
+          if (!Array.isArray(annotationPayload.result) && Array.isArray(annotationPayload.results)) {
+            annotationPayload.result = annotationPayload.results;
+          }
+
           // 最小化对齐 Label Studio Server 的字段（DataMate 侧会原样存储）
           const taskId = typeof currentTask?.id === "number" ? currentTask.id : Number(currentTask?.id) || null;
           const fileId = currentTask?.data?.file_id || currentTask?.data?.fileId || null;