Could a Railway engineer clarify the platform contract for manual Restart (not Redeploy)? This is a general documentation question, not a request to change any service.

The deployments reference describes Restart as restarting the process inside the container:

https://docs.railway.com/deployments/reference#restart

The recovery guide describes the existing container:

https://docs.railway.com/guides/roll-back-bad-deploy#rollback-vs-redeploy-vs-restart

But the Agent SDK guide says ephemeral files disappear on deploy or restart:

https://docs.railway.com/guides/claude-agent-sdk-app

For a single-replica Docker-image service with an existing attached volume:

1. Does manual Restart guarantee preservation of runtime-created files and runtime changes to the entrypoint in the writable root filesystem, or can it recreate/reset that filesystem?
2. Does the old process tree completely exit before the entrypoint runs again, with the volume already mounted?
3. What SIGTERM/grace/SIGKILL behavior applies specifically to manual Restart? Is RAILWAY_DEPLOYMENT_DRAINING_SECONDS relevant to that action?
4. If preservation is not guaranteed, is there a supported way to stop application writers gracefully and copy an ephemeral directory to the existing volume before the old filesystem is discarded?

A successful individual restart test or reuse of the same image would not establish a preservation guarantee. Please distinguish guaranteed behavior from best effort, including failure/host-replacement paths. No project identifiers, logs, credentials or customer data are included. Thank you.