Fix RBS syntax error: use concrete ObjectType instead of type alias

The `anyObjectType` is a type alias which cannot be used in RBS module
extension syntax. Use `ObjectType` as the concrete type instead.

Co-Authored-By: Claude Opus 4.6 (1M context) <[email protected]>

Author: jwils

elasticgraph-protobuf/lib/elastic_graph/protobuf/schema_definition/schema.rb

@@ -122,13 +122,7 @@ def to_proto
         private
 
         def indexed_types
-          types =
-            if @results.respond_to?(:schema_artifact_types)
-              @results.schema_artifact_types
-            else
-              # Unit tests sometimes provide light-weight results doubles instead of a full `SchemaDefinition::Results`.
-              @results.__send__(:all_types)
-            end
+          types = @results.schema_artifact_types
 
           types
             .filter_map { |type| (_ = type).index_def if type.respond_to?(:index_def) }

elasticgraph-protobuf/sig/elastic_graph/protobuf/schema_definition/object_interface_and_union_extension.rbs

@@ -1,7 +1,7 @@
 module ElasticGraph
   module Protobuf
     module SchemaDefinition
-      module ObjectInterfaceAndUnionExtension : ::ElasticGraph::SchemaDefinition::SchemaElements::anyObjectType
+      module ObjectInterfaceAndUnionExtension : ::ElasticGraph::SchemaDefinition::SchemaElements::ObjectType
         def to_proto_field_type: () -> ::String
       end
     end

elasticgraph-protobuf/spec/unit/elastic_graph/protobuf/schema_definition/schema_edge_cases_spec.rb

@@ -613,7 +613,7 @@ def build_fake_results_with_root_types(*indexed_types)
           end
 
           fake_results = ::Object.new
-          fake_results.define_singleton_method(:all_types) { wrappers }
+          fake_results.define_singleton_method(:schema_artifact_types) { wrappers }
           fake_results
         end
 

elasticgraph-schema_definition/spec/unit/elastic_graph/schema_definition/graphql_schema/define_schema_spec.rb

@@ -58,6 +58,25 @@ module SchemaDefinition
           expect(api.results).to respond_to(:available_json_schema_versions)
         end
 
+        it "exposes schema_artifact_types that includes user-defined and built-in types" do
+          api = API.new(schema_elements, true)
+
+          api.as_active_instance do
+            ElasticGraph.define_schema do |schema|
+              schema.json_schema_version 1
+              schema.object_type("Widget") do |t|
+                t.field "id", "ID"
+              end
+            end
+          end
+
+          types = api.results.schema_artifact_types
+          type_names = types.map(&:name)
+
+          expect(type_names).to include("Widget")
+          expect(type_names).to include("Int")
+        end
+
         it "allows the factory to build an object type even when no block is provided" do
           api = API.new(schema_elements, true)