Add changelog for 2.6.0

CHANGELOG.md

+## 2.6.0 (2025-05-25)
+
+### Added (1 change)
+
+- [Introduce `publish-policy-bundle` template](https://gitlab.com/components/opentofu/-/commit/c3621f7b8016cc57f3434ee164fa0b74f27e71ee) ([merge request](https://gitlab.com/components/opentofu/-/merge_requests/301))
+
+### Changed (1 change)
+
+- [Refactor runtime tooling into gitlab-tofu-ctl](https://gitlab.com/components/opentofu/-/commit/2a6f60823496d875ddb1930ac4f037f138afd6dd) ([merge request](https://gitlab.com/components/opentofu/-/merge_requests/300))
+
 ## 2.6.0-rc1 (2025-05-25)
 
 ### Added (1 change)