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/agents/components/AgentTryoutPanel.vue

@@ -17,6 +17,7 @@ import { computed, onBeforeUnmount, onMounted, ref, watch } from 'vue';
 import {
   CHAT_DOCUMENT_SUPPORTED_FORMATS,
   ChatTimeline,
+  defaultAssistantAvatar,
 } from '@easyflow/common-ui';
 import { BrushCleaning } from '@easyflow/icons';
 import { copyTextToClipboard } from '@easyflow/utils';
@@ -395,6 +396,7 @@ async function handleReject(payload: ChatTimelineToolApprovalPayload) {
       />
       <ChatTimeline
         v-else
+        :assistant-avatar="agent.avatar || defaultAssistantAvatar"
         :items="timelineItems"
         :document-loader="loadAgentChatDocument"
         :image-loader="loadAgentChatImage"