Externally defined subtypes are not resolved when referenced through the root

Given the setup below, the parser only resolves Animal and AnimalFarmEntry. The parser should also resolve Cat and Dog.

api.yaml

openapi: 3.0.0
info:
  title: Sample API
  description: API description in Markdown.
  version: 1.0.0
paths:
  /farm:
    get:
      summary: Get the animal farm.
      description: Optional extended description in Markdown.
      responses:
        200:
          description: OK
          content:
            application/json:
              schema:
                $ref: 'schema.yaml#/components/schemas/AnimalFarm'

schema.yaml

components:
  schemas:
    Dog:
      allOf:
        - $ref: '#/components/schemas/Animal'
        - type: object
          properties:
            breed:
              type: string
    Cat:
      allOf:
        - $ref: '#/components/schemas/Animal'
        - type: object
          properties:
            breed:
              type: string
    Animal:
      type: object
      discriminator:
        propertyName: className
      required:
        - className
      properties:
        className:
          type: string
        color:
          type: string
          default: red
    AnimalFarm:
      type: array
      items:
        $ref: '#/components/schemas/AnimalFarmEntry'
    AnimalFarmEntry:
      type: object
      properties:
        animal:
          $ref: "#/components/schemas/Animal"

Reproduce the issue with the referenced api.yaml and schema.yaml files, then trace the parser's external-reference resolution from AnimalFarm through Animal. Verify the completed behavior by checking that both Cat and Dog are resolved when referenced through the root schema.