google-gemini/gemini-cli ? reverse-engineered prompt

Build me a command-line tool that brings Google's Gemini AI right into my terminal. I want an AI agent I can chat with to help me with my coding and automation tasks. It should be able to understand my codebase, help me debug issues, and even generate new code from a prompt. Also give it built-in tools so it can read local files, run shell commands, and use Google Search to get current information so its answers aren't stale.

For authentication, please provide a few options. The main one should be a simple sign-in with a Google account, but it should also support using a standard Gemini API key or a Vertex AI setup for enterprise users.

Let's build it with TypeScript and make it easy for people to install via npm, Homebrew, or even run instantly with npx. It should also work non-interactively so it can be used in scripts, like for automating pull request reviews in a GitHub Action.