Some polish today: embed a nerd font, add better help and error handling.

I'm pretty happy overall with the approach I'm taking for web UI:

• Spin up a web server with Axum (Rust) for static content and a websocket
• Intentionally simple front-end (Tailwind+Preact). No build step, no business logic

The executable is 1.8MB (Windows) and nearly half of that is the font and Tailwind.