fix the issue that lost prev observation memory in toolExpert bug (#2136)

[cinjoseph]

…136)

Description

Close #2136

How Has This Been Tested?

prompt after fix

human: 最近消息记录:
Question: 使用get_current_system_time获取当前时间戳 
Thought: {
  "thought": "用户希望使用get_current_system_time工具来获取当前的时间戳。",
  "tool_name": "get_current_system_time",
  "args": {}
} 
Observation: 1731575527 
用户输入: Read the result data of the dependent steps in the above historical message to complete the current goal:使用format_time_stamp将时间戳转换为'yy-mm-dd'格式

output after fix

full stream output:
{
  "thought": "为了满足用户需求，需要先从历史消息中提取出当前的时间戳，然后使用format_time_stamp工具将其转换成指定的日期格式。",
  "tool_name": "format_time_stamp",
  "args": {
    "timestamp_str": "1731575527"
  }
}

>>>>>>>>LuBan Action report: 
execution succeeded,
24:11:14 17:12:07

Snapshots:

Include snapshots for easier review.

Checklist:

• My code follows the style guidelines of this project
• I have already rebased the commits and make the commit message conform to the project standard.
• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• Any dependent changes have been merged and published in downstream modules

[yhjun1026]

r+

[Aries-ckt]

Thanks for your contribution. r+

[Aries-ckt]

Close #2136