Separated list_agents() from session management (#4111)

### What problem does this PR solve?


### Type of change

- [x] Documentation Update

docs/references/http_api_reference.md

 
 Success:
 
-```text
+```json
 This is a test to verify the file download feature.
 ```
 
 
 ---
 
-## CHAT SESSIONS
+## SESSION MANAGEMENT
 
 ---
 
 ```json
 {
     "code": 102,
-    "message": "Name can not be empty."
+    "message": "Name cannot be empty."
 }
 ```
 
 ---
 
-### Update session
+### Update chat assistant's session
 
 **PUT** `/api/v1/chats/{chat_id}/sessions/{session_id}`
 
   The ID of the associated chat assistant.
 - `session_id`: (*Path parameter*)  
   The ID of the session to update.
-- `"name"`: (*Body Parameter), `string`  
+- `"name"`: (*Body Parameter*), `string`  
   The revised name of the session.
 
 #### Response
 
 ---
 
-### List sessions
+### List chat assistant's sessions
 
 **GET** `/api/v1/chats/{chat_id}/sessions?page={page}&page_size={page_size}&orderby={orderby}&desc={desc}&name={session_name}&id={session_id}`
 
 
 ---
 
-### Delete sessions
+### Delete chat assistant's sessions
 
 **DELETE** `/api/v1/chats/{chat_id}/sessions`
 
 Asks a specified chat assistant a question to start an AI-powered conversation.
 
 :::tip NOTE
-
 - In streaming mode, not all responses include a reference, as this depends on the system's judgement.
 - In streaming mode, the last message is an empty message:
-
-  ```text
+  ```json
   data:
   {
     "code": 0,
     "data": true
   }
   ```
-
 :::
 
 #### Request
 #### Response
 
 Success without `session_id`:
-```text
+```json
 data:{
     "code": 0,
     "message": "",
 
 Success with `session_id`:
 
-```text
+```json
 data:{
     "code": 0,
     "data": {
 Asks a specified agent a question to start an AI-powered conversation.
 
 :::tip NOTE
-
 - In streaming mode, not all responses include a reference, as this depends on the system's judgement.
 - In streaming mode, the last message is an empty message:
-
-  ```text
+  ```json
   data:
   {
     "code": 0,
     "data": true
   }
   ```
-
 :::
 
 #### Request
   The parameters in the begin component.
 #### Response
 success without `session_id` provided and with no parameters in the `begin` component:
-```text
+```json
 data:{
     "code": 0,
     "message": "",
 ```
 Success with `session_id` provided and with no parameters in the `begin` component:
 
-```text
+```json
 data:{
     "code": 0,
     "message": "",
 }
 ```
 Success with parameters in the `begin` component:
-```text
+```json
 data:{
     "code": 0,
     "message": "",
 
 ---
 
+## AGENT MANAGEMENT
+
+---
+
 ### List agents
 
 **GET** `/api/v1/agents?page={page}&page_size={page_size}&orderby={orderby}&desc={desc}&name={agent_name}&id={agent_id}`

docs/references/python_api_reference.md

 
 ---
 
-## CHAT SESSIONS
+## SESSION MANAGEMENT
 
 ---
 
 
 ---
 
+## AGENT MANAGEMENT
+
+---
+
 ### List agents
 
 ```python