Refresh AI region list after editor content loads

- Extract AI region scanning into a reusable utility with unit coverage.

- Refresh AI region dropdown state after drafts, reports, default templates, and selected templates write HTML into the editor.

- Keep the existing MutationObserver path for later DOM edits and inserted AI regions.

- Add E2E coverage for existing template AI regions appearing on initial report editor load.

- Update README, AGENTS, report editor, progress, and testing docs for AI region synchronization behavior.

README.md

@@ -201,6 +201,7 @@ cp .env.example .env.local
 - 本地存储封装和系统设置兼容。
 - 默认报告模板结构和字段配置。
 - 模板 HTML 导出包字段库元数据。
+- AI 区域扫描和报告编辑器加载后同步。
 - 打印导出入口。
 - 后端权限策略、AI 入参和语音代理帧处理。