Wait for a new container to finish setting up before entering it

container-up.sh starts the dev container in a scope of its own, so
distrobox enter finds it running and skips its wait for distrobox-init.
On a fresh install, init was still setting up passwordless sudo when
dev-container.sh ran sudo dnf install, and sudo asked for a password
with no terminal to read it from. container-up.sh now waits for
container_setup_done itself, and the container's sudo calls use -n,
so a password prompt fails at once with a clear message.

Fixes #9

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

setup/dev-container.sh

@@ -45,9 +45,9 @@ fi
 "$distrobox" enter dev -- bash -c '
 set -euo pipefail
 echo "installing ${#@} packages (already-installed ones are skipped)"
-sudo dnf install -y -q "$@" 2>&1 | { grep -vE "is already installed|^Nothing to do|^$" || true; }
+sudo -n dnf install -y -q "$@" 2>&1 | { grep -vE "is already installed|^Nothing to do|^$" || true; }
 # OpenVR programs built here (the pointer helper and probe) look for the runtime at /opt/steamvr.
-[ -e /opt/steamvr ] || sudo ln -s /run/host/opt/steamvr /opt/steamvr
+[ -e /opt/steamvr ] || sudo -n ln -s /run/host/opt/steamvr /opt/steamvr
 echo "dev container ready: $(. /etc/os-release; echo $PRETTY_NAME), glibc $(ldd --version | head -1 | grep -oE "[0-9.]+$")"
 ' dev "$@"
 EOF