Fix download model progress display when in parallel

Progress is displayed incorrectly (in the same place) when multiple models are downloaded in parallel.

```
var m = model.GetModel("gemma3:4b");
var x = model.GetModel("Gemma2-2b");
var taskM = model.DownloadAsync(m.Name);
var taskX = model.DownloadAsync(x.Name);
Task.WaitAll(taskM, taskX);
```

It would be nice to have final location displayed as well.