Windows install requires the full MSVC toolchain for fs-ext, which win32 never actually calls / Windows 安装被迫为从未调用的 fs-ext 拉起整套 MSVC 工具链

[frailove]

Environment / 环境

• Windows 11, Node 24, pnpm 11

• No Visual Studio / Build Tools installed (clean contributor machine)

• Windows 11，Node 24，pnpm 11

• 未安装 Visual Studio / Build Tools（干净的开发者机器）

What happens / 现象

pnpm install fails hard: fs-ext@2.1.1 (added in c58097a) has no prebuilt
binaries and must be compiled with node-gyp, so every Windows contributor now
needs the full "Desktop development with C++" toolchain (cl.exe + Windows SDK)
just to install the repo — for a binding that is never invoked on this platform.

pnpm install 直接失败：fs-ext@2.1.1（引入于 c58097a）没有预编译二进制，
必须用 node-gyp 本地编译。这意味着每一位 Windows 贡献者都要装上完整的
“使用 C++ 的桌面开发”工具链（cl.exe + Windows SDK）才能完成安装——
而这个原生绑定在 Windows 平台上根本不会被调用。

Root cause / 根因

packages/session/session-persistence-jsonl/src/lease.ts imports
{ flock } from 'fs-ext' at module top level, but on win32 the lock is a named
kernel semaphore via koffi (win32.ts) — the flock() code path is POSIX-only.
So the import is the only thing dragging the native build onto Windows.

packages/session/session-persistence-jsonl/src/lease.ts 在模块顶层
import { flock } from 'fs-ext'，但 win32 上的锁是通过 koffi 实现的
命名内核信号量（见 win32.ts）——flock() 代码路径仅在 POSIX 上执行。
也就是说，把这个原生编译依赖拖到 Windows 上的，仅仅是一行顶层 import。

The browser worker deployment already stubs fs-ext for exactly this reason,
which confirms non-POSIX deployments don't need the binding.

浏览器 worker 部署正是出于这个原因把 fs-ext 桩掉了，这也印证了
非 POSIX 部署并不需要这个绑定。

Suggested fixes / 建议修法（任选其一）

1. Lazy-import fs-ext inside the POSIX branch of
   SessionWriteLease.acquire() / release() (await import('fs-ext')).
   On win32 the module is never loaded, and allowBuilds: fs-ext: false
   becomes safe for Windows contributors. Smallest possible change.

2. 在 POSIX 分支内改为动态导入 fs-ext（SessionWriteLease.acquire() /
   release() 中使用 await import('fs-ext')）。win32 上该模块永远不会被
   加载，Windows 贡献者就可以安全地设置 allowBuilds: fs-ext: false。
   这是改动最小的方案。

3. Alternatively, move fs-ext behind a POSIX-only platform package, following
   the existing native/landlock-run pattern (linux-only packages that
   cleanly skip on other platforms).

4. 或者，参照现有的 native/landlock-run 模式（仅 Linux 的包在其他平台上
   干净地跳过），把 fs-ext 收进一个仅 POSIX 的平台包里。

Optionally, CONTRIBUTING.md could also document "VS Build Tools" as a Windows
prerequisite for as long as the compile step exists.

另外，只要编译步骤还存在，CONTRIBUTING.md 也可以顺手补充说明
Windows 需要 "VS Build Tools" 作为前置条件。