batman

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.

cmd/spreadlab/main.go

@@ -0,0 +1,9 @@
+// Command spreadlab will serve the spreadlab dashboard. For now it only
+// proves the module builds; the HTTP server arrives in milestone 2.
+package main
+
+import "fmt"
+
+func main() {
+	fmt.Println("spreadlab: engine under construction (milestone 1)")
+}