[Feature] More flexible `AgentHistory` for user `observation` and `user-takeover`

[gaomeng1900]

Feature Description / 功能描述

observation and user-takeover may need to be added to memory. Current history item only store actions. Either allow non-action in history or add non-action fields before or after an action.

Community Communication / 社区沟通

• I will be polite and respectful. / 我会保持礼貌与尊重。
• I will share constructive, actionable suggestions. / 我会提供建设性、可行动的建议。
• I have read the CODE_OF_CONDUCT.md and CONTRIBUTING.md. / 我已阅读行为准则。