[BUG] docker compose publish rejects short-form port mapping

Description

Running docker compose publish fails when a service uses the short-form port
syntax:

ports:
  - ${DASHBOARD_PORT:-3000}:3000

Error:

'services[whoami].ports[0]' expected a map or struct, got "string"

The short-form syntax is valid per the Compose spec
and works with docker compose up.
The OCI artifact encoder/decoder requires the long form:

ports:
  - target: 3000
    published: "${DASHBOARD_PORT:-3000}"

Steps To Reproduce

1. Create the file:

cat > compose.yaml <<'EOF'
services:
  whoami:
    image: docker.io/traefik/whoami:v1.11
    ports:
      - ${DASHBOARD_PORT:-3000}:3000
EOF

2. Publish:

docker compose publish <registry>/<image>:<tag>

Compose Version

$ docker-compose version
Command 'docker-compose' not found, but can be installed with:
sudo snap install docker          # version 28.4.0, or
sudo apt  install docker-compose  # version 1.29.2-6
See 'snap info docker' for additional versions.

$ docker compose version
Docker Compose version v5.1.0

Docker Environment

$ docker info
Client: Docker Engine - Community
 Version:    29.3.0
 Context:    default
 Debug Mode: false
 Plugins:
  buildx: Docker Buildx (Docker Inc.)
    Version:  v0.31.1
    Path:     /usr/libexec/docker/cli-plugins/docker-buildx
  compose: Docker Compose (Docker Inc.)
    Version:  v5.1.0
    Path:     /usr/libexec/docker/cli-plugins/docker-compose

Server:
 Containers: 0
  Running: 0
  Paused: 0
  Stopped: 0
 Images: 119
 Server Version: 4.9.3
 Storage Driver: overlay
  Supports d_type: true
  Native Overlay Diff: true
  Using metacopy: false
  Supports shifting: false
  Supports volatile: true
  Backing Filesystem: extfs
 Cgroup Driver: systemd
 Cgroup Version: 2
 Plugins:
  Volume: local
  Network: bridge macvlan ipvlan
  Log: k8s-file none passthrough journald
 Swarm: inactive
 Runtimes: crun ocijail runsc crun-wasm kata krun runc runj youki
 Default Runtime: crun
 Init Binary: 
 containerd version: 
 runc version: 
 init version: 
 Security Options:
  seccomp
   Profile: default
  rootless
 Kernel Version: 6.6.87.2-microsoft-standard-WSL2
 Operating System: ubuntu
 OSType: linux
 Architecture: amd64
 CPUs: 8
 Total Memory: 7.557GiB
 Name: DENEC1
 ID: 22893162-076d-4bf1-b265-666029302de0
 Docker Root Dir: /home/karna/.local/share/containers/storage
 Debug Mode: false
 Experimental: true
 Live Restore Enabled: false
 Product License: Apache-2.0

Anything else?

I'm using podman with docker-compose-plugin. Docker Engine is not installed.
Docker CLI use podman thanks to export DOCKER_HOST="unix://${XDG_RUNTIME_DIR}podman/podman.sock"
I don't think it change anything but for transparentsy.

I have used an AWS ECS for my test.

Start by reproducing the reported docker compose publish command with the short-form ports entry, then trace the publish path into the OCI artifact encoder/decoder described in the issue. No files or tests are named, so locate the relevant port conversion and its existing long-form handling; done means the short-form mapping publishes successfully without breaking long-form ports.