Description of Problem

When installed via gitops-operator, argocd-agent should use a downstream image. As reported on internal Slack (https://redhat-internal.slack.com/archives/C01RQH8KQ87/p1756141778048559), it is currently using a placeholder image.

Two changes we can make:

A) Argo CD operator should read the agent image from an env var (similar to how it works for argo cd images)

See 'getArgoContainerImage' for an example of the mechanism we use to determine the downstream image for argo cd (using GetEnv of 'ARGOCD_IMAGE').

Likely the logic should go in `buildPrincipalImage`

B) Our OpenShift GitOps build should inject the Konflux-built image into CSV

Once the ability to read argocd agent image is added to argocd-agent, we need to ensure the built image is updated in the openshift gitops csv.

If I am not mistaken, this is updated via this script: https://github.com/rh-gitops-midstream/release/blob/b248e1321ac14db623e0f1b27f748ef103e547b6/containers/gitops-operator-bundle/patch-bundle.py#L104

Acceptance Criteria

• argocd-operator should support reading default argocd agent image via env var
• rh-gitops-mistream-release repository is updated to support injecting argo cd agent image into CSV (via env var)