…olume mode

In run-script-step, the _temp directory was being copied to the workflow pod,
but the _github_home and _github_workflow directories were not being moved
from their temporary location to the /github directory structure where they
are expected by GitHub Actions.

This caused event.json to be missing at /github/workflow/event.json, breaking
actions that depend on GITHUB_EVENT_PATH.

The fix adds a setup step that copies _github_home and _github_workflow from
/__w/_temp/ to /github/ after copying the temp directory to the pod, matching
the behavior of run-container-step and prepareJobScript.

Uses cp -r instead of symlinks to avoid symlink validation errors when copying
files back from the pod to the runner.