feat(signing): 统一演示文书库并支持下载签名原图

clinical-web/src/views/workbench/signing/index.vue

@@ -261,8 +261,9 @@ async function loadTaskDetail(id: string | null) {
         throw detailResult.reason
       }
 
-      selectedTask.value = detailResult.value
-      signingAnswers.value = { ...(detailResult.value.fieldAnswers ?? {}) }
+      const detail = detailResult.value
+      selectedTask.value = detail
+      signingAnswers.value = { ...(detail?.fieldAnswers ?? {}) }
 
       if (eventsResult.status === 'fulfilled') {
         taskEvents.value = eventsResult.value
@@ -465,6 +466,8 @@ async function handleTaskAction(action: SigningTaskAction) {
 
     if (artifact) {
       await downloadArtifact(artifact)
+    } else if (isSigningMockEnabled) {
+      ElMessage.info('原型环境不生成 PDF，可在下方「签署文件」中下载签名原图')
     } else {
       ElMessage.info('当前任务暂无签署后 PDF')
     }