update changelogs

Author: dsinghvi

fern/products/cli-api-reference/cli-changelog/2026-04-14.mdx

@@ -1,3 +1,9 @@
+## 4.70.0
+**`(feat):`** Enable `--push-diff` flag for `fern sdk preview` to push a preview diff
+branch to the SDK repo in addition to publishing to the preview registry.
+Adds `diff_url` to the JSON and text output for use by CI integrations.
+
+
 ## 4.69.0
 **`(feat):`** Improve auto-versioning prompts for better SDK version bump determination and changelog quality.
 Commit type now matches version bump severity, per-chunk changelog entries use category tags,