fix: Improper spawn of sh on Windows Powershell

[PramaYudhistira]

Fix CLI launcher on Windows by replacing sh-based entrypoint with cross-platform Node script

What's changed

• This PR attempts to replace the sh-based entry point with a node script that works on all platforms including Windows Powershell and CMD

Why

• Previously, when installing Codex globally via npm i -g @openai/codex, Windows resulted in a broken CLI issue due to the ps1 launcher trying to execute sh.exe.

• If users don't have Unix-style shell, running the command will fail as seen below since sh.exe can't be found

• Output:

& : The term 'sh.exe' is not recognized as the name of a cmdlet, function, script file, or operable program. Check the
spelling of the name, or if a path was included, verify that the path is correct and try again.
At C:\Users\{user}\AppData\Roaming\npm\codex.ps1:24 char:7
+     & "sh$exe"  "$basedir/node_modules/@openai/codex/bin/codex" $args
+       ~~~~~~~~
   + CategoryInfo          : ObjectNotFound: (sh.exe:String) [], CommandNotFoundException
   + FullyQualifiedErrorId : CommandNotFoundException

How

• By using a Node based entry point that resolves the path to the compiled ESM bundle and dynamically loads it using native ESM

• Removed dependency on platform-specific launchers allowing a single entrypoint to work everywhere Node.js runs.

Result

Codex CLI now supports cross-platform and launches correctly via:

• macOS / Linux
• Windows PowerShell
• GitBash
• CMD
• WSL

Directly addresses #316

[github-actions]

All contributors have signed the CLA ✍️ ✅
_{Posted by the CLA Assistant Lite bot.}

[PramaYudhistira]

I have read the CLA Document and I hereby sign the CLA

[PramaYudhistira]

I have given a description of the issue here
#316

[tibo-openai]

looks good, ty!