fix: 'HandoffTool' object has no attribute 'agent'

[Li-shi-ling]

在调用 HandoffTool 工具时，出现了 "HandoffTool 对象没有 'agent' 属性" 的错误。经过排查发现，问题出现在 HandoffTool 的 init 方法中。在 self.agent = agent 赋值之后，调用 super().init() 会导致 self.agent 属性被意外覆盖或删除。
Fixes #5004

Modifications / 改动点

改变了astrbot.core.agent.handoff文件
将self.agent = agent移动到super().__init__之后

    def __init__(
        self,
        agent: Agent[TContext],
        parameters: dict | None = None,
        tool_description: str | None = None,
        **kwargs,
    ) -> None:

        # Avoid passing duplicate `description` to the FunctionTool dataclass.
        # Some call sites (e.g. SubAgentOrchestrator) pass `description` via kwargs
        # to override what the main agent sees, while we also compute a default
        # description here.
        # `tool_description` is the public description shown to the main LLM.
        # Keep a separate kwarg to avoid conflicting with FunctionTool's `description`.
        description = tool_description or self.default_description(agent.name)
        super().__init__(
            name=f"transfer_to_{agent.name}",
            parameters=parameters or self.default_parameters(),
            description=description,
            **kwargs,
        )

        # Optional provider override for this subagent. When set, the handoff
        # execution will use this chat provider id instead of the global/default.
        self.provider_id: str | None = None
        self.agent = agent

• This is NOT a breaking change. / 这不是一个破坏性变更。

Screenshots or Test Results / 运行截图或测试结果

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Checklist / 检查清单

• [ X ] 😊 如果 PR 中有新加入的功能，已经通过 Issue / 邮件等方式和作者讨论过。/ If there are new features added in the PR, I have discussed it with the authors through issues/emails, etc.
  没有新功能
• [ X ] 👀 我的更改经过了良好的测试，并已在上方提供了“验证步骤”和“运行截图”。/ My changes have been well-tested, and "Verification Steps" and "Screenshots" have been provided above.
  验证步骤在iss里面,运行截图在上方
• [ X ] 🤓 我确保没有引入新依赖库，或者引入了新依赖库的同时将其添加到了 requirements.txt 和 pyproject.toml 文件相应位置。/ I have ensured that no new dependencies are introduced, OR if new dependencies are introduced, they have been added to the appropriate locations in requirements.txt and pyproject.toml.
  没有引入
• [ X ] 😮 我的更改没有引入恶意代码。/ My changes do not introduce malicious code.
  没有引入

Summary by Sourcery

错误修复：

• 确保 HandoffTool 在基类初始化之后仍然保留其 agent 属性，以避免出现“object has no attribute agent”（对象没有 agent 属性）的错误。

Original summary in English

Summary by Sourcery

Bug Fixes:

• Ensure HandoffTool retains its agent attribute after base class initialization to avoid 'object has no attribute agent' errors.

- 修复在初始化过程中丢失 `HandoffTool.agent` 引用的问题，该问题会导致运行时错误：`'HandoffTool' object has no attribute 'agent'`。

Original summary in English

Summary by Sourcery

错误修复：

• 确保 HandoffTool 在基类初始化之后仍然保留其 agent 属性，以避免出现“object has no attribute agent”（对象没有 agent 属性）的错误。

Original summary in English

Summary by Sourcery

Bug Fixes:

• Ensure HandoffTool retains its agent attribute after base class initialization to avoid 'object has no attribute agent' errors.

[dosubot]

Related Documentation

Checked 1 published document(s) in 1 knowledge base(s). No updates required.

^{How did I do? Any feedback?}  

[sourcery-ai]

Hey - 我在这里给出了一些总体反馈：

• 建议在 self.agent = agent 附近加一条简短注释，说明这行代码必须放在 super().__init__() 之后赋值，因为父类的初始化方法会覆盖属性，这样可以避免以后重构时无意中再次引入这个 bug。

给 AI Agent 的提示

请根据本次代码审查中的评论进行修改：

## 总体评论
- 建议在 `self.agent = agent` 附近加一条简短注释，说明这行代码必须放在 `super().__init__()` 之后赋值，因为父类的初始化方法会覆盖属性，这样可以避免以后重构时无意中再次引入这个 bug。

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Original comment in English

Hey - I've left some high level feedback:

• Consider adding a short comment near self.agent = agent explaining that it must be assigned after super().__init__() because the parent initializer overwrites attributes, so future refactors don’t accidentally reintroduce the bug.

Prompt for AI Agents

Please address the comments from this code review:

## Overall Comments
- Consider adding a short comment near `self.agent = agent` explaining that it must be assigned after `super().__init__()` because the parent initializer overwrites attributes, so future refactors don’t accidentally reintroduce the bug.

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[Li-shi-ling]

这个bug藏的好深！我前半段时间一直以为是其他部位有什么操作将agent给去掉了
然后一直在研究SubAgentOrchestrator的走向
直到发现Context里的SubAgentOrchestrator管理器
就开始用插件测试，然后就发现在__init__阶段就出问题了

[Dt8333]

LGTM
合并前可能需要重新跑一下action确认无问题。