GitHub Actions: Early August 2026 Updates [GA]

### Value Prop

These GitHub Actions updates give you sharper visibility and tighter control over your CI/CD workflows. A new REST API lets your team check runner version deprecation timelines before they become a problem, while a new `vulnerability-alerts` read permission for `GITHUB_TOKEN` enables least-privilege access to Dependabot alerts. Four new `job` context properties also make it easier for reusable workflows to know their own source identity at runtime — so your shared workflows can reference exactly where they came from.

### Expected Outcome

Teams that rely on GitHub Actions can proactively plan runner upgrades instead of reacting to deprecation notices, reducing disruption to their pipelines. Finer-grained token permissions help organizations enforce security best practices without sacrificing access to the data their workflows need. Reusable workflow authors gain the runtime context they need to build more self-aware, maintainable automation.

未指明任何仓库文件、测试或实现入口。首先阅读 issue 中对 runner deprecation API、vulnerability-alerts 的 GITHUB_TOKEN 权限以及四个 job context 属性的描述；该 issue 未定义代码变更或具体的完成测试。

由索引模型根据 Issue 内容生成。