refactor(either): enhance throw error info

flake.nix

@@ -180,7 +180,7 @@
             };
           eitherN = tn:
             let
-              combine = a: b: if b == null then a else "[${a}]: ${b}";
+              combine = a: b: if a == null then b else "[${a}]: ${b}";
               logContexts = map (t: t.logContext or null) tn;
               # Function to pair two lists, combining their corresponding elements
               pairList = listA: listB: lib.lists.zipListsWith combine listA listB;