Support argv-safe Windows command shims in JavaScript shell mode

[konard]

Reproduction

The JavaScript package's exact-argv mode is ideal for native executables:

new ProcessRunner({ mode: "exec", file, args })

On Windows, command shims such as VS Code's code.cmd require a shell. The shell spec accepts only a completed command string:

new ProcessRunner({ mode: "shell", command })

There is no supported executable-plus-args form that delegates Windows command-line construction to Node. The exported quote() helper uses POSIX single quotes, which cmd.exe does not recognize, so consumers cannot safely assemble arbitrary arguments themselves.

Requested interface

Please support { mode: "shell", file, args } with platform-correct argument handling, or expose a Windows-safe command builder for the cmd.exe shell path.

Downstream workaround

link-assistant/formal-ai#990 routes asynchronous native executable boundaries through command-stream, but temporarily retains child_process.spawn(file, args, { shell: true }) for its Windows-only code.cmd --install-extension ... boundary.