openai/codex ? reverse-engineered prompt

I want to create a coding assistant that runs in the terminal. It should be a lightweight, local-first agent for developers to get quick answers without leaving their command line. A key part of the experience is making it super easy to install, maybe as a Homebrew cask or an npm global package for Mac, Windows, and Linux.

When the tool starts, it should display a nice splash screen. The main authentication method should be signing in with a ChatGPT account, so users can leverage their existing Plus or Team subscriptions directly. Avoid making API key setup the default flow. The whole application should feel fast and responsive, like a native tool. For the tech stack, let's use Rust since it compiles down to a single, portable binary. You can set up the project structure for me.