feat: migrate to golang

internal/service/exec_unix.go

@@ -0,0 +1,11 @@
+//go:build !windows
+
+package service
+
+import "os"
+
+// isExecutable checks the Unix executable bit, matching Python's
+// os.access(v, os.X_OK) check in ServiceConfig.validate_executable_path.
+func isExecutable(info os.FileInfo) bool {
+	return info.Mode()&0o111 != 0
+}