Doc generation: can't relatively-link to a decorator

If I write a doc comment like this, under the assumption that this comment is rendered to `reference/data-types.md`:

```typespec
/**
* Details applied to a package definition by the [`@package`](./decorators#@TypeSpec.Protobuf.package) decorator.
*/
model PackageDetails {
// ...
}
```

The actual result is that the link is mangled:

The (generated) Markdown itself is also mangled:

I'm _pretty sure_ that what's happening is that the `@` symbol in the link fragment is being treated as if it were a JSDoc-style tag, and the subsequent contents of the line are removed.