docs(notes): record hosted Windows runtime decision, retire the proposal

The failover runbook's Windows switch scope returns to the native Windows jobs:
remove the Python runtime eligibility sentences, the pool Python prerequisite,
and the proposal links. The #3629 self-hosted Python runtime proposal is
retired (deleted as obsolete after its unmeasured-throughput run), and a new
implemented note records that the Windows x64 runtime lane stays on
GitHub-hosted Windows with the evidence and alternatives. Bilingual sidecars
re-recorded.

python/development.zh.md

@@ -15,8 +15,6 @@ pnpm exec tsx scripts/build-exe-for-python-sdk.ts
 
 所需 `lib/` 产物已存在时使用 `--skip-build`；如需选择平台，请使用 `--targets=node24-linux-x64,node24-linux-arm64,node24-macos-arm64,node24-macos-x64,node24-win-x64`。每个目标都应在其原生架构上构建。产物写入 `dist-exe/`，脚本会将所选载体同步到 `python/sdk-runtime/`。Windows 会生成 `.exe` 与 `-rg.exe`；macOS 构建还会同步 `node-pty` 所需的配套 spawn 辅助程序。
 
-仅用于 CI 的 Windows x64 构建可在 `DSH_CI_FAILOVER_WINDOWS=selfhosted` 时使用自托管池：只有同仓库、非 fork、非 Dependabot 的拉取请求符合条件。作业将 Python 3.10 下载到私有临时目录而不在 Windows 中注册它，隔离构建缓存与测试环境，并在成功或失败后删除该目录。发布与手动构建、Linux 与 macOS 目标，以及 SDK wheel 辅助作业仍使用托管运行器。镜像前提与验证限制见[运行器隔离提案](../.agents/notes/proposed/process/2026-09-06-python-runtime-windows-selfhosted.zh.md)。
-
 ## 验证 SDK
 
 请将虚拟环境放在 `python/` 之外，安装测试组，然后运行 Python 测试套件：