Add support for installation on OpenBSD

What variant of Codex are you using?

CLI

What feature would you like to see?

When running codex as installed from npm the following error is reported:

file:///home/user/.npm-global/lib/node_modules/@openai/codex/bin/codex.js:70
  throw new Error(`Unsupported platform: ${platform} (${arch})`);
        ^

Error: Unsupported platform: openbsd (x64)
    at file:///home/user/.npm-global/lib/node_modules/@openai/codex/bin/codex.js:70:9
    at ModuleJob.run (node:internal/modules/esm/module_job:343:25)
    at async onImport.tracePromise.__proto__ (node:internal/modules/esm/loader:665:26)
    at async asyncRunEntryPointWithESMLoader (node:internal/modules/run_main:117:5)

Node.js v22.22.0

With the minor work-around from https://github.com/openai/codex/issues/12337 or presumably just using Rust 1.91 on OpenBSD 7.8, the Codex CLI seems to build and work fine.

Ideally Codex would make its way into OpenBSD Ports one day, but it would be nice to be able to just install it with whatever installation processes is normal for Codex.

Additional information

To explore feasibility, I attempted to draft an OpenBSD Port for Codex: https://github.com/DeciSym/openbsd-port-codex