Fix Windows Codex executable resolution via shutil.which()

[grayson-k]

Problem

On Windows, Codex installed via npm may only be available as codex.cmd / codex.ps1.

subprocess.run(["codex", ...])

can fail with:

FileNotFoundError: [WinError 2]

even when codex --version works fine in PowerShell.

Fix

Resolve the executable path first using:

shutil.which(binary)

and use the resolved path for both subprocess.run() and exec_or_spawn().

Testing

Tested with:

• Windows
• codex-cli 0.153.3
• ucode 0.1.0+83.g2f993ce