feat: Hardcode version into install scripts at release time.

[charlielye]

• To avoid the fiddly requirement of setting both the VERSION env var, while also putting the version in the curl path, we now hardcode it at release time into the script.
• The root installer, when manually uploaded, then sets the VERSION to default to nightly (if not given).
• Carefully crafted banner and text to fit on 80 char width terminals. Because it's important we support those.

I may also have updated the ascii art a bit. I doubt I'll be allowed to keep it because it's so OUTRAGEOUSLY 80's neon cyberpunk. But it's trivial to swap the banner if want something more brand fitting.