[Request]: Describe the available platforms when an image has no variant for the requested one

### Feature or enhancement request details

Reopening #2229 as an enhancement request, following the feedback there.

### Description

Running an image that only ships linux/amd64 fails with `Error: platform linux/arm64`. This message gives no clue if the image hasn't arm64 variant, which platforms it does have, or that `--arch amd64` / `--platform linux/amd64` makes it run under Rosetta.

For example, when I run
```
MH='mailhog/mailhog:v1.0.1@sha256:8d76a3d4ffa32a3661311944007a415332c4bb855657f4f6c57996405c009bea'
container image pull "$MH"
container run -d --name mh -p 8025:8025 "$MH"
```

I get the following message: `"Error: platform linux/arm64"`

But I was expecting something more meaningful like `"image docker.io/mailhog/mailhog@sha256:8d76... has no linux/arm64 variant (available: linux/amd64). Use --arch amd64 or --platform linux/amd64 to run it with Rosetta."`

Therefore, instead of returning a bare message, it could be enhanced to list the platforms it actually has and mention the flag that works.

### Code of Conduct

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

No source file or test is named in the issue. Start by tracing the container run platform-validation error and how image manifest platforms are read; done means the failure identifies the missing platform, lists available platforms, and mentions the applicable --arch or --platform option, with coverage for the shown single-variant image case.

Written by the indexing model from the issue text.