Image OCI config is dropped when building actor runtime spec #300

Expected Behavior

When an actor is created from an ActorTemplate, the workload container should inherit the
environment variables baked into its image's OCI config (Config.Env), the same way docker run
and containerd/CRI do.

Actual Behavior

The image's OCI config is discarded when building the actor's runtime spec. The process only ever
sees a hardcoded PATH plus whatever env the ActorTemplate sets explicitly; the image's ENV
directives never reach the process.

Steps to Reproduce the Problem

1. Build and push an image with ENV vars set:

   FROM busybox:1.36
   ENV DEMO_VAR=example

   docker buildx build --platform linux/arm64 -t <registry>/env-demo:v1 --push .
   

2. Create an ActorTemplate that references the image:

   apiVersion: ate.dev/v1alpha1
   kind: ActorTemplate
   metadata:
     name: env-demo
     namespace: <ns>
   spec:
     workerPoolRef: { name: <pool>, namespace: <ns> }
     pauseImage: <pause-image@sha256:...>
     snapshotsConfig: { location: <gs://.../env-demo> }
     runsc: { arm64: { url: <...>, sha256Hash: <...> }, amd64: { url: <...>, sha256Hash: <...> } }
     containers:
       - name: app
         image: <registry>/env-demo@sha256:...   # the image from step 1, digest-pinned
         command: ["/bin/sh","-c","echo DEMO_VAR=$DEMO_VAR; env; sleep 3600"]

3. Inspect the actor process's environment which should be forwarded to stdout. Note that it DEMO_VAR is empty.