AI Security Detections on PRs [GA]

### Value Prop

Building on the Public Preview, the GA release of AI Security Detections on PRs delivers a polished experience for AI-powered security findings in pull requests.

### Expected Outcome

GitHub's AI security detections are now generally available, providing production-grade coverage for languages currently unsupported by CodeQL (PHP, Shell, HCL, JSP, Blazor), enabling security teams to enforce AI-found vulnerabilities as merge blockers, and delivering an improved developer experience with clearer alert presentation in pull requests.

此路线图 issue 未指定任何仓库文件、测试或入口点，因此请先定位 pull request 上 AI 安全检测的实现。完成意味着交付 GA 体验，包括覆盖 PHP、Shell、HCL、JSP 和 Blazor、会阻止合并的安全发现，以及更清晰的 pull request 警报。

由索引模型根据 Issue 内容生成。