[Request]: `container image load` cannot load legacy Docker tarfiles created by the Google Jib Gradle plugin.

### Feature or enhancement request details

When I use the reproduction example below to create a simple jib image, I'm unable to load the resulting tarfile into `container`.

```console
% gradle jibBuildTar

> Task :jibBuildTar

...

BUILD SUCCESSFUL in 6s
2 actionable tasks: 1 executed, 1 up-to-date

% container image load -i ./build/jib-image.tar
Error: /var/folders/6k/tnyh0vfd07z0f9mr5cg7zs5r0000gn/T/4278F53C-9ED8-4F46-9354-F2B465C970C9/oci-layout
```

Reproducer: [20260417-tiny-jib.tgz](https://github.com/user-attachments/files/26841228/20260417-tiny-jib.tgz)

We could consider handling this in a utility somewhere within container that converts an unpacked docker image archive into an OCI archive in-place, instead of adding support for the legacy docker format in the Containerization image store itself.

### Code of Conduct

- [x] I agree to follow this project's Code of Conduct

Start by unpacking 20260417-tiny-jib.tgz and reproducing `container image load -i ./build/jib-image.tar`; inspect the legacy archive contents and the reported `oci-layout` failure. Done means the Jib-generated tarfile loads successfully through the image command without the current error.

Written by the indexing model from the issue text.