Update changelogs from fern repo (#1733)

Co-authored-by: fearthecowboy <[email protected]>

Author: fern-support

fern/products/sdks/overview/csharp/changelog/2025-10-31.mdx

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+## 2.6.0
+**`(feat):`** Significant improvements to class/property/namespace tracking, collisions reduced.
+Generated snippets and examples are far more accurate.
+Resolved a case where files with duplicate names were clobbered.
+Implicit namespaces are consistent across .NET frameworks now.
+Eliminated unnecessary namespace and scoping in generated code.
+Significant fixes to generated code for Pagination scenarios.
+
+