chore: add github actions for marking bug issues stale

[ocetars]

Motivation / 动机：

为项目添加自动化 Issue 管理功能。随着项目发展，Issue 数量不断增加，一些长期未解决的 bug 可能被遗忘或失去关注。通过引入 stale workflow，可以自动识别和处理长时间不活跃的 bug issue，提高项目维护效率。

解决的问题：

• 自动标记90天无活动的 bug issue 为 stale 状态
• 30天后自动关闭仍无活动的 stale issue
• 避免重要 bug 被遗忘，同时清理无效/过时的 issue
• 支持手动触发和预览模式，便于维护者控制
• 提供友好的中英双语提示，改善用户体验

Modifications / 改动点

新增文件：

• .github/workflows/stale.yml - 新增 GitHub Actions stale workflow

实现的功能：

• 🎯 精确目标管理：仅处理带有 bug 标签的 Issue，不干扰其他类型 Issue 或 PR

• ⏰ 智能时间策略：90天无活动标记为 stale，额外30天观察期后自动关闭

• 🔄 自动恢复机制：启用 remove-stale-when-updated，Issue 有新活动时自动移除 stale 标签

• 🌍 双语支持：提供中英双语的标记和关闭消息模板

• 🛠️ 调试友好：支持 workflow_dispatch 手动触发和 dry-run 预览模式

• 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

验证步骤：

1. ✅ 检查 workflow 文件语法正确，无 YAML 格式错误
2. ✅ 验证 dry-run 模式能正确预览将要处理的 Issue
3. ✅ 确认只处理带有 bug 标签的 Issue

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Checklist / 检查清单

• 😊 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.
• 👀 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.
• 🤓 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.
• 😮 我的更改没有引入恶意代码。/ My changes do not introduce malicious code.

Summary by Sourcery

配置一个自动化的 GitHub Actions 工作流，用于给长期未活动的缺陷（bug）问题打标并关闭。

New Features:

• 引入一个定时运行的 stale 工作流，仅针对标记为 bug 的 Issue，并排除 Pull Request。
• 添加手动触发的 workflow_dispatch 支持，并提供可选的 dry-run 模式，用于预览 stale 处理行为。

Enhancements:

• 定义用于标记和关闭陈旧缺陷问题的未活动阈值、标签以及双语通知消息。

Original summary in English

Summary by Sourcery

Configure an automated GitHub Actions workflow to label and close long-inactive bug issues.

New Features:

• Introduce a scheduled stale workflow that targets only issues labeled as bug and excludes pull requests.
• Add manual workflow_dispatch support with an optional dry-run mode for previewing stale processing behavior.

Enhancements:

• Define inactivity thresholds, labels, and bilingual notification messages for marking and closing stale bug issues.

[sourcery-ai]

Hey - 我在这里给出了一些整体性的反馈：

• 目前陈旧问题（stale-issue）和关闭问题（close-issue）的提示信息里只说问题会在“某个时间段后”被关闭；建议明确写出 30 天的时间窗口，与配置的 days-before-issue-close 保持一致，避免让用户产生困惑。
• debug-only 标志只在 workflow_dispatch 下生效，并且默认值是 true，这意味着手动触发的运行默认是干跑（dry-run）；如果维护者会经常通过手动运行来做真实的清理操作，可能更合适把 dry-run 的默认值设为 false。

给 AI Agent 的提示

Please address the comments from this code review:

## Overall Comments
- The stale-issue and close-issue messages say issues will be closed "in a certain period of time"; consider explicitly mentioning the 30‑day window to match the configured `days-before-issue-close` and avoid confusion for users.
- The `debug-only` flag is only active for `workflow_dispatch` and defaults to `true`, which means manual runs are dry-run by default; if maintainers will commonly use manual runs for real cleanup, you might want to default `dry-run` to `false` instead.

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Original comment in English

Hey - I've left some high level feedback:

• The stale-issue and close-issue messages say issues will be closed "in a certain period of time"; consider explicitly mentioning the 30‑day window to match the configured days-before-issue-close and avoid confusion for users.
• The debug-only flag is only active for workflow_dispatch and defaults to true, which means manual runs are dry-run by default; if maintainers will commonly use manual runs for real cleanup, you might want to default dry-run to false instead.

Prompt for AI Agents

Please address the comments from this code review:

## Overall Comments
- The stale-issue and close-issue messages say issues will be closed "in a certain period of time"; consider explicitly mentioning the 30‑day window to match the configured `days-before-issue-close` and avoid confusion for users.
- The `debug-only` flag is only active for `workflow_dispatch` and defaults to `true`, which means manual runs are dry-run by default; if maintainers will commonly use manual runs for real cleanup, you might want to default `dry-run` to `false` instead.

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