[docs] a bit addition info for pd disaggregation (#1434)

Author: zhuzilin

docs/en/advanced/pd-disaggregation.md

@@ -3,3 +3,5 @@
 slime supports Prefill and Decode disaggregation (PD Disaggregation).
 
 You can set the number of servers used for Prefill by setting the `--prefill-num-servers` argument.
+
+We recommand using PD Disaggregation for multi-turn/agentic RL training.

docs/zh/advanced/pd-disaggregation.md

@@ -3,3 +3,5 @@
 slime 支持 Prefill 和 Decode 的分离部署 (PD Disaggregation)。
 
 可以通过设置 `--prefill-num-servers` 参数来指定用于 Prefill 的服务器数量。
+
+我们推荐在多轮或 agentic RL 训练中开启 PD 分离。