TypeError in `normalize_error_paths` with federated routers

We are using WunderGraph's Cosmo Router for GraphQL federation. When the resolver fails to bulk load data in an array context from a federated subgraph, the router will include an `@` in the error paths for those errors, instead of an array index integer. From my research, this is semi-standard with federated routers like Cosmo and Apollo Router. When processing the response in these cases, the graphql client will fail with the following error:

```
TypeError: no implicit conversion of String into Integer
--
0: ruby/3.2.5/lib/ruby/gems/3.2.0/gems/graphql-client-0.26.0/lib/graphql/client/errors.rb:27:in `block (2 levels) in normalize_error_paths'
1: ruby/3.2.5/lib/ruby/gems/3.2.0/gems/graphql-client-0.26.0/lib/graphql/client/errors.rb:24:in `each'
2: ruby/3.2.5/lib/ruby/gems/3.2.0/gems/graphql-client-0.26.0/lib/graphql/client/errors.rb:24:in `block in normalize_error_paths'
3: ruby/3.2.5/lib/ruby/gems/3.2.0/gems/graphql-client-0.26.0/lib/graphql/client/errors.rb:21:in `each'
4: ruby/3.2.5/lib/ruby/gems/3.2.0/gems/graphql-client-0.26.0/lib/graphql/client/errors.rb:21:in `normalize_error_paths'
...
```

it's happening on this line in `Errors.normalize_error_paths` while validating the paths exist in the data:

```ruby
current = current[key]
```

in this context, `current` is an array, but `key` is `"@"`, which is causing a type error.

## Reproducing the error:

```ruby
errs_with_at = [{"message"=>"boom", "locations"=>[{"line"=>1, "column"=>113}], "path"=>["records", "@", "item"]}]
GraphQL::Client::Errors.normalize_error_paths({"records"=>[{"item"=>nil}]}, errs_with_at)
```

### Expected result:

```ruby
[{"message"=>"boom", "locations"=>[{"line"=>1, "column"=>113}], "path"=>["records", "@", "item"], "normalizedPath"=>["data", "records", "@", "item"]}]
```

### Actual result

```
TypeError: no implicit conversion of String into Integer
from /Users/tlubitz/.asdf/installs/ruby/3.2.5/lib/ruby/gems/3.2.0/gems/graphql-client-0.26.0/lib/graphql/client/errors.rb:27:in `block (2 levels) in normalize_error_paths'
```

By contrast, the same invocation works if you replace `"@"` with e.g. `0`:

```ruby
errs = [{"message"=>"boom", "locations"=>[{"line"=>1, "column"=>113}], "path"=>["records", 0, "item"], "normalizedPath"=>["data", "records", 0, "item"]}]
GraphQL::Client::Errors.normalize_error_paths({"records"=>[{"item"=>nil}]}, errs)

[{"message"=>"boom", "locations"=>[{"line"=>1, "column"=>113}], "path"=>["records", 0, "item"], "normalizedPath"=>["data", "records", 0, "item"]}]
```