feat: 统一聊天助手头像

- 工作流运行状态、智能体正式聊天与试运行展示助手头像

- 新增默认机器人头像及消息、空状态回退组件

easyflow-ui-admin/app/src/views/ai/workflow/components/WorkflowChatPage.vue

@@ -15,7 +15,7 @@ import type {
 import { computed, nextTick, onBeforeUnmount, onMounted, ref } from 'vue';
 import { useRoute } from 'vue-router';
 
-import { ChatTimeline } from '@easyflow/common-ui';
+import { ChatTimeline, defaultAssistantAvatar } from '@easyflow/common-ui';
 
 import {
   ArrowLeft,
@@ -931,8 +931,10 @@ function executionTraceText(
       <template v-else>
         <ChatTimeline
           class="workflow-chat__timeline"
+          :assistant-avatar="defaultAssistantAvatar"
           :items="timelineItems"
           :empty-text="emptyText"
+          :empty-title="descriptor.title || '工作流'"
           :copy-action="copyMessage"
           :copyable="(item) => item.parts.some((part) => part.content)"
         >