Parsing dataset uri is broken if namespace starts with `@v`

### Description

Parsing logic of `parse_dataset_uri(uri)` function is broken as it misses the case where namespace can start with `@v` e.g `@vlad` and since version separator is also `@v` it incorrectly parses the uri which causes pulling dataset command for example to fail.

### Version Info

```Text
0.25.2.dev63+g21d5399c4.d20250829
Python 3.12.4
```