fix(devcontainer): drop stale vscode remoteUser

[NichSchlagen]

Problem

Opening the repo in the dev container fails immediately:

Error: unable to find user vscode: no matching entries in passwd file
Error: An error occurred setting up the container.

The container itself starts fine; it breaks as soon as the Dev Containers CLI tries to open a shell as remoteUser.

Cause

The vscode user came from the ghcr.io/devcontainers/features/common-utils:2 feature. That feature was removed in cc4337c (#12805), but remoteUser and the usermod -a -G mock vscode onCreateCommand were left behind. ghcr.io/terrapkg/builder has no vscode user of its own:

$ podman run --rm ghcr.io/terrapkg/builder:frawhide grep -c vscode /etc/passwd
0

So the dev container has been broken for everyone since that commit.

Fix

Drop remoteUser and the onCreateCommand and run as root, which also makes the usermod into the mock group unnecessary. This matches how CI already builds packages with the very same image — GitHub Actions containers run as root, and mock works fine there (see .github/workflows/json-build.yml).

Re-adding the common-utils feature would be the alternative if an unprivileged user is wanted, but that seems to go against the intent of #12805.

Verification

With this change the container comes up, and a real package build inside it completes as root:

podman run --rm --privileged -v "$PWD":/workspace:z -w /workspace \
  ghcr.io/terrapkg/builder:frawhide bash -c 'anda build -c terra-rawhide-x86_64 ...'

[nothingneko]

do we want to allow this to run as root or not, @Owen-sz thoughts?

[madonuko]

I don't see an issue?