Update changelogs from fern repo (#2489)

Co-authored-by: dsinghvi <10870189+dsinghvi@users.noreply.github.com>

Author: fern-support

fern/products/cli-api-reference/cli-changelog/2025-12-03.mdx

@@ -1,3 +1,7 @@
+## 2.18.1
+**`(fix):`** Improve enum validation error messages to show which enum value has an invalid name. When the API source is OpenAPI, the error message now includes guidance about using the `x-fern-enum` extension to specify valid names.
+
+
 ## 2.18.0
 **`(feat):`** Add `--fernignore` CLI option for remote generation. This allows users to provide a custom `.fernignore` file that will replace the existing one on the main branch during remote generation. The custom fernignore will be applied during generation and committed to the repository.