And this "supercomputer", how will it account for people's wants and desires? People aren't parts in a machine, intended to be used to further some arbitrary ends, they are sovereign beings capable of making decisions and fulfilling their own wants. No centralized system can account for me deciding I want a ham sandwich instead of turkey sandwich.
When you buy this sandwich, the planning system will count increase in this good's consumption and can balance its supply to meet demand.
OK, so.....welfare then? Or maybe a better term would be slave/forced labor. When people are denied the basic right of determining how they will work and for what gains, they call that slavery.
There are no welfare for idling, as well as forced labor - the state owns means of production so pays to its workers as corporations do now (but in more fairer way so the owner won't get 99% of the profit).
P.S. It is clear for almost everyone that technological unemployment is a final
stalemate for the free market! Of course this system have some advantages over central planning, but will be dead no matter how much do you like it (not certainly anywhere in the world - most likely regions like Silicon Valley will prosper under capitalism but be populated only with "technological elite")! Think realistically, not emotionally!