fix(model): Remove the validation that tool_call_id must be empty. (#497)

Author: junwen-lee

backend/domain/agent/singleagent/internal/agentflow/callback_reply_chunk.go

@@ -286,7 +286,7 @@ func concatToolsNodeOutput(ctx context.Context, output *schema.StreamReader[call
 		msgs := convToolsNodeCallbackOutput(cbOut)
 
 		for _, msg := range msgs {
-			if msg == nil || msg.ToolCallID == "" {
+			if msg == nil {
 				continue
 			}