amend! feat: add the `git ents auth` porcelain for managing push signers

feat: add the git ents auth porcelain for managing push signers

git ents auth fetches a remote’s refs/meta/auth, edits it through the signers helpers, and pushes it back as a clean compare-and-swap, and sets this machine up to produce the signed pushes the server requires.

feat: add a git-ents binary with an auth subcommand group feat: add git ents auth setup to configure this machine for signed pushes feat: add git ents auth list to show a remote’s authorized signers feat: add git ents auth add and remove to update and push the set feat: add git ents auth check to report authorization and client config feat: push the signer set with --force-with-lease and --force-if-includes refactor: parent signer-set updates on the current auth ref Assisted-by: Claude:claude-opus-4-8