[plugin-import-export] Prefix labels being applied to row fields and unnamed/unlabelled group fields in export fields dropdown

Describe the Bug.

Prefix labels are being applied to row fields and unnamed/unlabelled group fields in the Export Options Fields dropdown.

Example:

{
  type: 'row',
  fields: [
    {
      type: 'text',
      name: 'test1',
      label: 'Test1'
    },
    {
      type: 'text',
      name: 'test2',
      label: 'Test2'
    }
  ]
}

Suggested fix — Prefix labels should be removed in these instances. Change how fields are being reduced in packages/plugin-import-export/src/components/FieldsToExport/reduceFields.tsx

if (!isArrayOrBlocks && fieldHasSubFields(field)) {
  const affectsData = fieldAffectsData(field)

  return [
    ...fieldsToUse,
    ...reduceFields({
      disabledFields,
      excludeUnsortable,
      fields: field.fields,
      labelPrefix: affectsData
        ? combineLabel({
            field,
            prefix: labelPrefix,
          })
        : labelPrefix,
      path: createNestedClientFieldPath(path, field)
    })
  ]
}

Reproduction Steps

1. Install the plugin-import-export plugin
2. Enable the plugin-import-export plugin on a collection in the payload.config
3. In your collection, add the fields:

{
  type: 'row',
  fields: [
    {
      type: 'text',
      name: 'test1',
      label: 'Test1'
    },
    {
      type: 'text',
      name: 'test2',
      label: 'Test2'
    }
  ]
}

4. Open the exports modal/drawer on the collection list view and select Export
5. Select the fields defined in step 3 in the Export Options Fields dropdown

Environment Info

Payload: 3.85.1
Node.js: 22.17.0
Next.js: 16.2.6

Start in packages/plugin-import-export/src/components/FieldsToExport/reduceFields.tsx and trace how labels are reduced for row and unnamed group fields. Reproduce the Export Options Fields dropdown with the provided row-field configuration; done when those fields no longer display prefixed labels while other nested field labels retain their intended prefixes.