Well obviously ceramic discharge tubes achieve some sort of seal around wire feed throughs, but how? What material do they use for the wire and how is the seal made?

This may help you:
http://lamptech.co.uk/MH%20Ceramic.htm .
Also if you click on thee early lamps you can learn more about their specific construction.

This may help you:

Alright, I just looked at every last picture on this website, and it is very eye-opening! Thanks for recommending this, I will probably reference it in the future. Definitely answered my question.