[BUG] Duplicate fields returned when disable_objects set

What is the bug?

Fields are duplicated in search results when objects have disable_objects set to true.

How can one reproduce the bug?

1. Create the index with disable_objects: true, index a document and query using the PPL API

PUT test-disable-objects
{
  "mappings": {
    "properties": {
        "attributes": {
          "disable_objects": true,
          "type": "object"
        }
      }
  }
}

POST test-disable-objects/_doc
{
  "attributes": {
    "log.file.path": "/var/log/app.log"
  }
}

POST _plugins/_ppl
{
  "query" : "source=test-disable-objects"
}

2. This returns both an attributes struct field and a log.file.path string field:

{
  "schema": [
    {
      "name": "attributes",
      "type": "struct"
    },
    {
      "name": "attributes.log.file.path",
      "type": "string"
    }
  ],
  "datarows": [
    [
      {
        "log": {
          "file": {
            "path": "/var/log/app.log"
          }
        }
      },
      "/var/log/app.log"
    ]
  ],
  "total": 1,
  "size": 1
}

What is the expected behavior?

Fields should not be duplicated

What is your host/environment?

Opensearch 3.8.0

Do you have any screenshots?
If applicable, add screenshots to help explain your problem.

Do you have any additional context?

This causes fields to be duplicated in the Opensearch Dashboards Explore Logs app:

Interestingly, there is no attributes.logtag in that screenshot, which suggests the bug only presents itself when there are multiple layers of nesting.

Start by running the documented reproduction through the _plugins/_ppl API with an index using disable_objects: true, then trace how nested fields are assembled into the schema and data rows. Done means the attributes struct and nested attributes.log.file.path are not returned as duplicate fields, including the multi-level nesting case.