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/ChatTimelineItem.vue

@@ -1,7 +1,8 @@
 <script setup lang="ts">
 import type {
-  ChatTimelineItem,
+  ChatDocumentLoader,
   ChatImageLoader,
+  ChatTimelineItem,
   ChatTimelineMessageItem,
   ChatTimelineMessagePart,
   ChatTimelineToolApprovalPayload,
@@ -10,9 +11,10 @@ import type {
 import { computed, ref } from 'vue';
 
 import ChatThinkingBlock from '../chat-thinking/ChatThinkingBlock.vue';
+import ChatDocumentAttachments from './ChatDocumentAttachments.vue';
 import ChatErrorNotice from './ChatErrorNotice.vue';
-import ChatKnowledgeCard from './ChatKnowledgeCard.vue';
 import ChatImageAttachments from './ChatImageAttachments.vue';
+import ChatKnowledgeCard from './ChatKnowledgeCard.vue';
 import ChatMessageToolbar from './ChatMessageToolbar.vue';
 import ChatTextBlock from './ChatTextBlock.vue';
 import ChatTimelineStatusRow from './ChatTimelineStatusRow.vue';
@@ -20,13 +22,14 @@ import ChatToolCard from './ChatToolCard.vue';
 
 const props = defineProps<{
   approvalLoading?: boolean;
+  assistantActionsVisible?: boolean;
   copyable?: boolean;
   copyAction?: (item: ChatTimelineMessageItem) => boolean | Promise<boolean>;
-  regenerable?: boolean;
-  regenerateDisabled?: boolean;
-  assistantActionsVisible?: boolean;
+  documentLoader?: ChatDocumentLoader;
   imageLoader?: ChatImageLoader;
   item: ChatTimelineItem;
+  regenerable?: boolean;
+  regenerateDisabled?: boolean;
   variantLoading?: boolean;
 }>();
 
@@ -161,6 +164,12 @@ function handleCopyAction() {
         :image-loader="imageLoader"
         compact
       />
+      <ChatDocumentAttachments
+        v-if="messageItem.documents?.length"
+        :items="messageItem.documents"
+        :document-loader="documentLoader"
+        compact
+      />
       <template v-for="part in getMessageParts(messageItem)" :key="part.id">
         <ChatThinkingBlock
           v-if="part.type === 'thinking'"
@@ -237,16 +246,16 @@ function handleCopyAction() {
   display: flex;
   flex-direction: column;
   gap: 8px;
-  max-width: min(78%, 680px);
   min-width: 0;
+  max-width: min(78%, 680px);
 }
 
 .chat-timeline-item__message {
   display: flex;
   flex-direction: column;
   gap: 8px;
-  max-width: min(78%, 680px);
   min-width: 0;
+  max-width: min(78%, 680px);
 }
 
 .chat-timeline-item__message :deep(.chat-text-block),