Update docs for Ansible hardening roles

CHANGELOG.md

@@ -1,5 +1,24 @@
 # Changelog
 
+## [Unreleased]
+
+### Added
+
+- CIS-inspired Ansible hardening automation:
+  - RHEL 9 role and playbook.
+  - Debian 13 / Ubuntu 26.04 role and playbook.
+  - IBM AIX 7 role and playbook.
+- Shared sanitized Ansible inventory defaults for Linux and AIX examples.
+- Role-level task structure covering pre-checks, SSH, sudo, auditing, logging, services, filesystem controls, platform-specific settings, handlers, and post-check validation.
+
+### Changed
+
+- Updated repository, `infra-run`, and Ansible README files to describe the new hardening automation instead of placeholder-only Ansible structure.
+
+### Notes
+
+- Hardening content is CIS-inspired and intended for portfolio/lab use; production use requires environment-specific review and validation.
+
 ## [Initial Version]
 
 ### Added