math/rand/v2 (Go 1.22+) replaces the old math/rand: PCG generator,
no global Seed(), and rand.New(rand.NewPCG(seed, 0)) gives an isolated
deterministic stream. Each randomness consumer (graph, thresholds,
education sampling) will get its own stream so levers vary independently.
Tests live next to the code as *_test.go; 'go test ./...' runs them all.
'for i := range 100' is Go 1.22 range-over-int.
go.mod declares the module path (github.com/JustinZeus/spreadlab); every
import inside the repo is spelled relative to it. Layout follows the
standard Go shape: cmd/<binary>/main.go per executable, internal/ for
packages other modules may not import (the compiler enforces this).
No engine code yet, just a placeholder main that proves 'go build' works.