allOf is not properly merged

Given a schema that uses `allOf` to combine two different `object` schemas, the properties of the two schemas are not combined:

```json
{
"components": {
"schemas": {
"identifier": {
"type": "object",
"properties": {
"id": {"type": "string"}
}
},
"person": {
"allOf": [
{"$ref": "#/components/schemas/identifier"},
{
"type": "object",
"properties": {
"name": {
"type": "string"
}
}
}
]
}
}
}
}
```

Not 100% sure that schema validates, but it should be a good start.

Start by reproducing the provided OpenAPI schema in the project's schema parsing path and confirm whether the example validates. Trace how allOf schemas are combined, then verify that the resulting person schema exposes both id and name properties.

Written by the indexing model from the issue text.