Immutable Releases

GitHub has an [Immutable Releases](https://docs.github.com/en/code-security/supply-chain-security/understanding-your-software-supply-chain/immutable-releases) setting that prevents tags being modified after they've been pushed. Please could you enable it for both this repo and the mirrors? I know pre-commit already treats tags as immutable, but currently we use commit hashes to ensure that Alice's installed v6.0.0 always matches Bob's v6.0.0.