feat(addons): Enable GitOps layer addons for cloudfront-exposure

Parent: #699

## Addons

- [ ] `argo_events` — event sources and sensors for triggering workflows
- [ ] `argo_rollouts` — progressive delivery (canary, blue-green deployments)
- [ ] `kargo` — environment promotion pipelines (dev → staging → prod)

## Notes

- `argo_events` and `argo_rollouts` have no ingress — just enable them
- `kargo` has a dashboard that may need ingress with path rewrite for cloudfront mode
- All three are already defined in `gitops/addons/registry/gitops.yaml`
- Spoke clusters also enable `argo_rollouts` (see hub-config.yaml spoke1/spoke2)

Start with gitops/addons/registry/gitops.yaml to compare the existing definitions for argo_events, argo_rollouts, and kargo, then check hub-config.yaml for the spoke1/spoke2 argo_rollouts settings. Verify that all three addons are enabled for cloudfront-exposure, and confirm whether kargo’s dashboard requires the noted ingress path rewrite.

Written by the indexing model from the issue text.