* Add pkgmgr branch close subcommand, extend CLI parser wiring, and add unit tests for branch handling and version version-selection logic (see ChatGPT conversation: https://chatgpt.com/share/693762a3-9ea8-800f-a640-bc78170953d1)
* Add branch closing helper and --close flag to release command, including CLI wiring and tests (see https://chatgpt.com/share/69374aec-74ec-800f-bde3-5d91dfdb9b91)
* Add preview-first release workflow and extended packaging support (see ChatGPT conversation: https://chatgpt.com/share/693722b4-af9c-800f-bccc-8a4036e99630)
* Implement unified release helper with preview mode, multi-packaging version bumps, and new integration/unit tests (see ChatGPT conversation 2025-12-08: https://chatgpt.com/share/693722b4-af9c-800f-bccc-8a4036e99630)