Include codegen crate name in generated file header
diff --git a/src/gen/fold.rs b/src/gen/fold.rs
index ed6b3c0..e7b5964 100644
--- a/src/gen/fold.rs
+++ b/src/gen/fold.rs
@@ -1,4 +1,5 @@
-// THIS FILE IS AUTOMATICALLY GENERATED; DO NOT EDIT
+// This file is @generated by syn-internal-codegen.
+// It is not intended for manual editing.
 
 #![allow(unreachable_code)]
 #[cfg(any(feature = "full", feature = "derive"))]