Update changelogs from fern repo (#5301)

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

Author: fern-support

fern/products/cli-api-reference/cli-changelog/2026-05-01.mdx

@@ -1,3 +1,25 @@
+## 5.7.0
+**`(internal):`** cli-v2: introduce a shared stdin/stdout abstraction so commands uniformly honor
+the Unix `-` marker on I/O flags (stdin for inputs, stdout for outputs), with a
+"`-` used at most once per command" guard and a JSON-or-path input helper that
+parses inline JSON first and falls back to a file read.
+
+
+**`(internal):`** cli-v2: `fern api compile --output -` now uses the shared stdio helper (behavior
+unchanged — still streams IR JSON to stdout).
+
+
+**`(feat):`** cli-v2: `fern sdk generate --api -` and `fern sdk preview --api -` now read the
+OpenAPI/AsyncAPI spec from stdin (e.g. `cat openapi.json | fern sdk generate
+--api - --org acme --target typescript --output ./sdk`).
+
+
+**`(feat):`** cli-v2: `fern api split --output -` prints the generated overlay/overrides for
+the matching spec to stdout as a preview, without modifying the workspace
+(no git-HEAD restore, no fern.yml updates). Requires `--api` to select a single
+spec.
+
+
 ## 5.6.1
 **`(fix):`** Fix translated docs pages failing to resolve shared snippets (`<Markdown src="..."/>` and `<Code src="..."/>`).
 Snippet references are now resolved before registering translations, with locale-aware loading that prefers