US construction productivity fell from 1970 to 2020 while the rest of the economy got more productive, and a 1-year-old startup called Unlimited Industries is trying to reverse that. Unlimited is managing $10 billion in data center and power plant projects, compressing design and engineering work that typically takes 18 months and 100,000 human hours into a single day. The team has set out to do for construction what SpaceX did for launch and Anduril did for defense: question every assumption…