Update changelogs from fern repo (#4429)

Co-authored-by: Swimburger <3382717+Swimburger@users.noreply.github.com>

Author: fern-support

fern/products/sdks/overview/csharp/changelog/2026-03-20.mdx

@@ -1,3 +1,12 @@
+## 2.49.0
+**`(feat):`** Add per-send timeout to prevent `SendAsync` hangs. A new `SendTimeout` property
+(default: 30 seconds) on `WebSocketConnection` wraps every `SendAsync` call with a
+linked `CancellationTokenSource` that fires `CancelAfter(SendTimeout)`. When the
+timeout elapses the connection is aborted and a `WebsocketException` is thrown,
+preventing a single dead connection from blocking the send lock for up to 30 minutes.
+See: https://github.com/dotnet/runtime/issues/125257
+
+
 ## 2.48.0
 **`(feat):`** Add bounded send queue with message expiration to `WebSocketConnection`. The
 unbounded `Channel<T>` queues are replaced with configurable bounded channels