add notes for to_dist field

docs/sphinx_doc/en/source/tutorial/201-agent.md

@@ -16,6 +16,8 @@ Each AgentBase derivative is composed of several key characteristics:
 
 * `sys_prompt` & `engine`: The system prompt acts as predefined instructions that guide the agent in its interactions; and the `engine` is used to dynamically generate a suitable prompt. For more details about them, we defer to [Prompt Engine](206-prompt).
 
+* `to_dist`: Used to create a distributed version of the agent, to support efficient collaboration among multiple agents. Note that `to_dist` a reserved field and will be automatically added to the initialization function of any subclass of `AgentBase`. For more details about `to_dist`, please refer to [Distribution](208-distribute).
+
 In addition to these attributes, `AgentBase` endows agents with pivotal methods such as `observe` and `reply`:
 
 * `observe()`: Through this method, an agent can take note of *message* without immediately replying, allowing it to update its memory based on the observed *message*.

docs/sphinx_doc/zh_CN/source/tutorial/201-agent.md

@@ -17,6 +17,8 @@
 
 * `sys_prompt`（系统提示）和`engine`（引擎）：系统提示作为预定义的指令，指导agent在其互动中的行为；而engine用于动态生成合适的提示。关于它们的更多细节，我们会在[提示引擎部分](206-prompt)讨论。
 
+* `to_dist`（分布式）：用于创建 agent 的分布式版本，以支持多 agent 的高效协作。请注意`to_dist`是一个保留字段，将自动添加到`AgentBase`所有子类的初始化函数中。关于 `to_dist` 的更多细节，请见[分布式部分](208-distribute)。
+
 除了这些属性，`AgentBase` 还为agent提供了一些关键方法，如 `observe` 和 `reply`：
 
 * `observe()`：通过这个方法，一个agent可以注意到消息而不立即回复，允许它根据观察到的消息更新它的记忆。