Set up Go module and move Rust to legacy

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

.gitignore

@@ -10,3 +10,7 @@ target/
 
 # Local brainstorming companion artifacts
 .superpowers/
+
+# Go
+/antidriftd
+*.test

cmd/antidriftd/main.go

@@ -0,0 +1,7 @@
+package main
+
+import "fmt"
+
+func main() {
+	fmt.Println("antidriftd")
+}

go.mod

@@ -0,0 +1,3 @@
+module antidrift
+
+go 1.26.3