add gemini example video resolves #256 , fix react agent tool_name build

[wozhapen]

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Checklist | 检查项

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• 添加react agent 调试 gemini 的过程视频 resolves 【Easy Issue/入门实战】Video Tutorial Recording/视频教学录制 #256
• 修复react agent 填充 tool_name 的bug

Please provide the path of test files and submit screenshots or files of the test results(fill in as needed): | 请填写测试文件路径并提供测试结果截图或文件(按需填写):

• fix tool_name
  

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