status command reports image availability for missing containers

When a container doesn't exist, the status command now checks whether the service image is present in the container runtime via 'container image inspect'. Output shows either '(image <ref> is available)' or '(image <ref> not pulled)'.

Support compose.override.yaml and docker-compose.override.yaml

Override files are detected alongside the base compose file using both known compose stems (docker-compose / compose) and both YAML extensions (.yml / .yaml). The override is deep-merged into the base configuration, with maps merged recursively and slices/scalars replaced outright.

Also adds a StringOrStringList type for the Command field, which now accepts either a single string or an array of strings in YAML — matching Docker Compose semantics.

update github workflow action versions

Fix GitHub Actions deprecation warnings

- Opt into Node.js 24 via FORCE_JAVASCRIPT_ACTIONS_TO_NODE24 env var
- Disable Go cache to avoid tar restore warnings on first run

handle run (as well as start)

workdir
command

move commands onto service