Extending a nested &:hover in a @define-placeholder is ignored.

```
@define-placeholder icon-holder {
color: #999;
&:hover { color: red; }
}
```

OUTPUT:

```
.icon-test1,
.icon-test2 {
color:#999
}
```

Reproduce the issue using the @define-placeholder example and inspect the plugin entry point where placeholder selectors are expanded. Confirm how nested &:hover rules are handled, then ensure the generated output retains the hover rule for each extended selector. Done means the example no longer drops the nested rule.

Written by the indexing model from the issue text.