feat: add webui http channel for chat and file upload

internal/agent/orchestrator.go

@@ -117,6 +117,24 @@ func (o *Orchestrator) HandleMessageWithFiles(ctx context.Context, chatID, userI
 	return o.handleMessageInternal(ctx, chatID, userID, text, files)
 }
 
+// UploadAndCacheFiles 上传文件到 LLM 并缓存 file_id，供后续同会话文本问答复用。
+// 该方法不会写入 messages 表，仅更新内存中的 pending file 上下文。
+func (o *Orchestrator) UploadAndCacheFiles(ctx context.Context, chatID, userID string, files []llm.InputFile) ([]string, error) {
+	if len(files) == 0 {
+		return nil, fmt.Errorf("no files provided")
+	}
+	uploadCtx := o.prepareFilePromptContext(ctx, files, nil)
+	if strings.TrimSpace(uploadCtx.FatalReason) != "" {
+		return nil, fmt.Errorf(uploadCtx.FatalReason)
+	}
+	ids := nonEmptyIDs(uploadCtx.FileIDs)
+	if len(ids) == 0 {
+		return nil, fmt.Errorf("file upload completed but no valid file_id returned")
+	}
+	o.appendPendingFiles(chatID, userID, uploadCtx.toPendingRefs())
+	return ids, nil
+}
+
 func (o *Orchestrator) handleMessageInternal(ctx context.Context, chatID, userID, text string, files []llm.InputFile) (string, error) {
 	// 为链路追踪设置唯一的 TraceID
 	traceID := logger.NewTraceID()