Display specific error and enable steps if Docker Model Runner is not running

[doringeman]

Before:

$ docker model status
Docker Model Runner is not running

Now:

$ docker model status
Docker Model Runner is not running

What's next:
    Enable Docker Model Runner via the CLI → docker desktop enable model-runner
    Enable Docker Model Runner via the GUI → Go to Settings->Features in development->Enable Docker Model Runner

Before:

$ docker model run ai/smollm2
Failed to list model: failed to list models: 503 Service Unavailable

Now:

$ docker model run ai/smollm2
Docker Model Runner is not running. Please start it and try again.


What's next:
    Enable Docker Model Runner via the CLI → docker desktop enable model-runner
    Enable Docker Model Runner via the GUI → Go to Settings->Features in development->Enable Docker Model Runner

To build and install locally:

make clean && make link