feat: 支持智能体文档附件与轻量读取

- 建立文档上传、异步读取、对象存储、补偿与聊天绑定闭环

- 按智能体 20K 上下文预算选择文档片段并保留稳定引用

- 统一聊天文件卡片、类型图标、草稿恢复与可靠下载

easyflow-ui-admin/packages/effects/common-ui/src/components/chat-timeline/ChatTimeline.vue

@@ -1,7 +1,8 @@
 <script setup lang="ts">
 import type {
-  ChatTimelineItem as ChatTimelineItemType,
+  ChatDocumentLoader,
   ChatImageLoader,
+  ChatTimelineItem as ChatTimelineItemType,
   ChatTimelineMessageItem,
   ChatTimelineToolApprovalPayload,
 } from './types';
@@ -14,6 +15,7 @@ const props = defineProps<{
   approvalLoading?: boolean;
   copyable?: (item: ChatTimelineMessageItem) => boolean;
   copyAction?: (item: ChatTimelineMessageItem) => boolean | Promise<boolean>;
+  documentLoader?: ChatDocumentLoader;
   emptyText?: string;
   imageLoader?: ChatImageLoader;
   items: ChatTimelineItemType[];
@@ -152,6 +154,7 @@ watch(
         :key="item.id"
         :assistant-actions-visible="isAssistantActionAnchor(item)"
         :item="item"
+        :document-loader="documentLoader"
         :image-loader="imageLoader"
         :approval-loading="approvalLoading"
         :copy-action="copyAction"