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/builder.ts

@@ -196,7 +196,7 @@ function removeStatusItem(items: ChatTimelineItem[], statusKey: string) {
   const index = items.findIndex(
     (item) => item.type === 'status' && item.statusKey === statusKey,
   );
-  if (index >= 0) {
+  if (index !== -1) {
     items.splice(index, 1);
   }
 }
@@ -341,7 +341,7 @@ export const ChatTimelineBuilder = {
     metadata?: Partial<ChatTimelineMessageItem>,
   ) {
     const text = normalizeText(content);
-    if (!text && !metadata?.images?.length) {
+    if (!text && !metadata?.images?.length && !metadata?.documents?.length) {
       return;
     }
     const item: ChatTimelineMessageItem = {
@@ -605,7 +605,7 @@ export const ChatTimelineBuilder = {
         item.role === 'assistant' &&
         item.roundId === roundId,
     );
-    if (targetIndex >= 0) {
+    if (targetIndex !== -1) {
       items.splice(targetIndex, 1, message);
     }
   },