no-mistakes(review): Correct CHANGELOG upgrade note: delete old helpers first

Author: dmealing

CHANGELOG.md

@@ -26,8 +26,10 @@ here.**
   `DecimalWire[.<Namespace>].g.cs` and `MetaNetValidation[.<Namespace>].g.cs` were the only
   emitted files without it, so a runner with no `GenStateDir` wrote them once and then logged
   `refusing to overwrite hand-written file` on every later run, leaving a stale copy (and the
-  `@precision`/`@scale` input check inside it) behind. Regenerate once; the marker is the only
-  change to the helpers' text.
+  `@precision`/`@scale` input check inside it) behind. A copy already on disk has no marker, so
+  regenerating alone keeps refusing it: delete the existing `DecimalWire*.g.cs` and
+  `MetaNetValidation*.g.cs` files, then regenerate. The marker is the only change to the
+  helpers' text.
 - The 1.1.0 entry's handler-code figure of 439 lines retired is corrected to about 460, as
   measured in one adopter's pull request.