[Bug] `hydrogen deploy`: `--env` and `--env-branch` are mutually exclusive

What is the location of your example repository?

https://github.com/Shopify/hydrogen/tree/main/templates/skeleton

Which package or tool is having this issue?

CLI

What version of that package or tool are you using?

@shopify/cli-hydrogen@11.1.16 & @shopify/cli@4.0.0

What version of React Router 7 are you using?

7.14.0

Steps to Reproduce

1. In Oxygen Admin, create a long-lived environment, e.g. staging with branch tag staging, exposed at a stable URL (e.g. https://staging-skeleton.hydrogen.shop/).

2. Locally, check out a different branch (e.g. a weekly release branch release/1.2.3):

   git checkout release/1.2.3
   
   

3. Try to deploy that working tree to the staging environment:

   shopify hydrogen deploy --env staging --env-branch release/1.2.3
   

   The CLI rejects this:

   --env-branch=release/1.2.3 cannot also be provided when using --env
   

4. Drop --env-branch and use only --env:

   shopify hydrogen deploy --env staging
   

   The deploy is forced to the environment's configured branch (staging); there is no way to deploy the release/1.2.3 working tree under the staging environment while preserving traceability of the source branch.

5. Drop --env and use only the deprecated flag:

   shopify hydrogen deploy --env-branch staging
   

   This flag is deprecated, and in CI (CI=1) it is also the only option, since --env is rejected with Can't specify an environment handle in CI.

Expected Behavior

Concretely, any of the following would resolve the gap:

• Allow --env and --env-branch to be combined. --env selects the environment record (URL, secrets, env vars); --env-branch overrides the deployment tag. Both should work in interactive and CI modes.
• Replace the deprecated --env-branch with a clearly-named successor (e.g. --deployment-tag) that composes with --env.
• Allow --env alone to deploy the working tree against the chosen environment, without coupling the deployment tag to the environment's configured branch.
  This would unblock release-train workflows where a team:
• cuts a release/X.Y.Z branch on a regular cadence,
• needs to QA each release at a fixed staging URL backed by stable secrets/env vars,
• and wants the deployment tag in Oxygen Admin to reflect the actual source branch (release/1.2.3), not a generic placeholder.
  The same flag combination must work in CI, since releases are typically deployed from automation rather than a developer's laptop.

Actual Behavior

There is no flag combination that lets a developer deploy an arbitrary local branch to a chosen environment handle:

• --env <handle> --env-branch <tag> → rejected by exclusive: ['env-branch'] in packages/cli/src/lib/flags.ts.
• --env <handle> alone → the deployment tag is taken from the environment's configured branch in Admin, ignoring the local checkout. There is no opt-out.
• --env-branch <tag> alone → works, but the flag is deprecated (--env-branch is deprecated. Use --env instead.) and is the only option allowed in CI today.
  The result is a forced choice between (a) reconfiguring the staging environment's branch in Oxygen Admin for every release, (b) renaming branches to match a fixed tag and losing release identity, or (c) relying on a deprecated flag with no announced successor that covers this case.

Start in packages/cli/src/lib/flags.ts, where the exclusive env-branch validation is mentioned, and reproduce the deploy commands with and without CI=1. Trace how the environment handle and deployment tag are passed through the CLI. Done means a chosen environment can be deployed with an explicit source tag in both interactive and CI modes without relying on the deprecated flag.