Stop using 'alpha-cli' moving tag

This breaks brew install --HEAD codex as the brew git client would try to fetch the tag and got a clobbering error

==> Fetching codex
==> Cloning https://github.com/openai/codex.git
Updating /Users/sluongng/Library/Caches/Homebrew/codex--git
From https://github.com/openai/codex
 ! [rejected]          alpha-cli  -> alpha-cli  (would clobber existing tag)
Error: codex: Failed to download resource "codex (HEAD)"
Failure while executing; `/usr/bin/env git fetch origin` exited with 1. Here's the output:
From https://github.com/openai/codex
 ! [rejected]          alpha-cli  -> alpha-cli  (would clobber existing tag)

And because of homebrew limitations, it's a bit hard to add a refspec to ignore this tag locally.

So instead of using a moving tag, could you please use a protected branch instead?
The general convention is that branches can be updated regularly, while tags aren't.

My current workaround is to manually wipe the tag before each homebrew update

git -C /Users/sluongng/Library/Caches/Homebrew/codex--git/ tag -d alpha-cli

_Originally posted by @sluongng in https://github.com/openai/codex/discussions/3025_