fix: select examples new graph load twice

[peng-shuo]

修复选择组件的例子中，画布加载两次的问题

📝 Description

将选择组件的例子中,

1. 逻辑部分的加载方式从类组件更改为函数式组件
2. 加上正确的生命周期开始注册，结束注销的方式
3. 解决由于重复加载后，出现的grid画面重复的问题（出现原因是两次重新加载期间没有正确的注销画布）

🖼️ Screenshot

Before	After
❌	✅

💡 Motivation and Context

🧩 Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)
• Enhancement (changes that improvement of current feature or performance)
• Refactoring (changes that neither fixes a bug nor adds a feature)
• Test Case (changes that add missing tests or correct existing tests)
• Code style optimization (changes that do not affect the meaning of the code)
• Docs (changes that only update documentation)
• Chore (changes that don't modify src or test files)

🔍 Self Check before Merge

• My code follows the code style of this project.
• My change requires a change to the documentation.
• I have updated the documentation accordingly.
• I have read the CONTRIBUTING document.
• I have added tests to cover my changes.
• All new and existing tests passed.

[gemini-code-assist]

Summary of Changes

Hello @peng-shuo, I'm Gemini Code Assist¹! I'm currently reviewing this pull request and will post my feedback shortly. In the meantime, here's a summary to help you and other reviewers quickly get up to speed!

此拉取请求旨在解决选择组件示例中画布重复加载的错误。通过将组件转换为函数式组件，并利用 useEffect 钩子实现画布的正确初始化和销毁，从而避免了画布实例的重复创建和网格重复显示的问题，提升了示例的稳定性和用户体验。

Highlights

• 组件重构: 将 SelectionExample 组件从类组件重构为函数式组件，以利用 React Hooks。
• 画布生命周期管理: 使用 useEffect 和 useRef 实现了画布实例的正确生命周期管理，确保在组件卸载时正确销毁画布。
• 解决重复加载问题: 修复了选择组件示例中画布重复加载导致网格重复显示的问题，通过在每次加载前正确注销旧画布来解决。

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[gemini-code-assist]

Code Review

本次 PR 将 SelectionExample 组件从类组件重构为了函数式组件，并使用 useEffect Hook 来管理 Graph 实例的生命周期。这个改动是正确的，通过在 useEffect 的清理函数中调用 graph.dispose()，有效地解决了之前因组件重复加载而导致的画布渲染两次的问题。代码实现清晰，遵循了现代 React 的最佳实践。我只发现了一个可以移除未使用变量的小改进点，具体请看我的评论。

[hustcc]

@peng-shuo 感谢！估计其他的 examples 也还是 class component 的写法，有兴趣都改掉吗？应该可以使用 ai 都解决。

[Copilot]

Copilot encountered an error and was unable to review this pull request. You can try again by re-requesting a review.

[peng-shuo]

@hustcc ok

@peng-shuo 感谢！估计其他的 examples 也还是 class component 的写法，有兴趣都改掉吗？应该可以使用 ai 都解决。

Ok，最新的提交已经将这个问题修复了