The previous assertion read the generated CLIProxy config.yaml directly via
getConfigPathForPort(). On the self-hosted CI runner this produced ENOENT even
though applyCliproxyRoutingStrategy returned 'config-only', indicating the
read path and write path diverged in the full test-suite context.
Verify persistence via loadUnifiedConfig() instead — that's the canonical
source mutateUnifiedConfig writes to, independent of regenerateConfig's
file-path resolution.