Update changelogs from fern repo (#4490)

Co-authored-by: iamnamananand996 <31537362+iamnamananand996@users.noreply.github.com>

Author: fern-support

fern/products/sdks/overview/rust/changelog/2026-03-22.mdx

@@ -1,3 +1,12 @@
+## 0.26.2
+**`(chore):`** Include all optional fields as `Option<T>` parameters in convenience constructors.
+Previously, `{variant}_with_{field}` constructors only accepted the promoted field and
+defaulted all other optional fields to `None`. Now they accept all other optional fields
+as `Option<T>` parameters, giving callers full control over all fields. For example,
+`assistant_with_tool_calls` now accepts `(content: Option<Content>, ..., tool_calls: Vec<ToolCall>)`
+instead of just `(tool_calls: Vec<ToolCall>)`.
+
+
 ## 0.26.1
 **`(fix):`** Fix convenience constructors for union variants whose optional fields have nested
 optional/nullable IR wrappers (e.g. `optional<nullable<string>>` from OpenAPI).