As others have said, there's all sorts of things an HTML renderer can do better than terminal: proper (not hacked) image handling on both input and output, rendering graphical results, graphs, better code highlighting and diffs, interactive elements, etc. But one thing that strikes me as especially important: a proper accessibility story with magnification, screen reader, TTS etc.

All the stuff people are hacking into TUIs is honestly a bit silly, they're actually very inefficient for high fidelity UIs. Having worked in it and on it before while @ GOOG, the actual renderer in Chromium is an optimized thing of beauty. It really makes sense to leverage it. Appropriately.

But all of the above could (should) be done as a locally hosted web page via the existing codex CLI launching a local web server... rather than shipping an electron binary with its own entire fork of Chromium.