Attempted to generate duplicate models with name "TypenameFieldnameItem"

Describe the bug
I stumbled on a weirdly specific bug that causes the generator to attempt to generate duplicate models.

Apparently we need:

• a OneOf type (A), which references an Object type (B)
• An object type (B) with an array-of-object field
• An Object type (C) for the array-of-object field
• array-of-C and C must be declared inline inside B

OpenAPI Spec File

This works

openapi: 3.0.3
info:
  title: Minimal example for error "Attempted to generate duplicate models"
  version: 1.0.0

components:
  schemas:
    Result:
      oneOf:
        - $ref: "#/components/schemas/ResultA"
      discriminator:
        propertyName: type
        mapping:
          "A": "#/components/schemas/ResultA"

    ResultA:
      type: object
      properties:
        things:
          type: array
          items:
            $ref: "#/components/schemas/ResultAThingsItem"

    ResultAThingsItem:
      type: object
      properties:
        name:
          type: string

paths:
  /something:
    get:
      summary: Returns a list of users.
      responses:
        '200':
          description: A successful response returning the list of users.
          content:
            application/json:
              schema:
                $ref: '#/components/schemas/Result'

This should be the same, but doesn't work:

openapi: 3.0.3
info:
  title: Minimal example for error "Attempted to generate duplicate models"
  version: 1.0.0

components:
  schemas:
    Result:
      oneOf:
        - $ref: "#/components/schemas/ResultA"
      discriminator:
        propertyName: type
        mapping:
          "A": "#/components/schemas/ResultA"

    ResultA:
      type: object
      properties:
        things:
          type: array
          items:
            type: object
            properties:
              name:
                type: string

paths:
  /something:
    get:
      summary: Returns a list of users.
      responses:
        '200':
          description: A successful response returning the list of users.
          content:
            application/json:
              schema:
                $ref: '#/components/schemas/Result'

Output:

$ pipx run openapi-python-client generate --path=example.yaml --overwrite
Generating <...>/minimal-example-for-error-attempted-to-generate-duplicate-models-client
Warning(s) encountered while generating. Client was generated, but some pieces may be missing

WARNING parsing GET /something within default.

Cannot parse response for status code 200 (Could not find reference in parsed models or enums), response will be omitted from generated client

Reference(ref='#/components/schemas/Result')

Unable to process schema /components/schemas/Result:

Attempted to generate duplicate models with name "ResultAThingsItem"

Failure to process schema has resulted in the removal of:
/components/schemas/ResultA
/components/schemas/Result

Schema(title=None, multipleOf=None, maximum=None, exclusiveMaximum=None, minimum=None, exclusiveMinimum=None, maxLength=None, minLength=None, pattern=None, maxItems=None, minItems=None, uniqueItems=None, maxProperties=None, minProperties=None, required=None, enum=None, const=None, type=<DataType.OBJECT: 'object'>, allOf=[], oneOf=[], anyOf=[], schema_not=None, items=None, prefixItems=[], properties={'name': Schema(title=None, multipleOf=None, maximum=None, exclusiveMaximum=None, minimum=None, exclusiveMinimum=None, maxLength=None, minLength=None, pattern=None, maxItems=None, minItems=None, uniqueItems=None, maxProperties=None, minProperties=None, required=None, enum=None, const=None, type=<DataType.STRING: 'string'>, allOf=[], oneOf=[], anyOf=[], schema_not=None, items=None, prefixItems=[], properties=None, additionalProperties=None, description=None, schema_format=None, default=None, nullable=False, discriminator=None, readOnly=None, writeOnly=None, xml=None, externalDocs=None, example=None, deprecated=None)}, additionalProperties=None, description=None, schema_format=None, default=None, nullable=False, discriminator=None, readOnly=None, writeOnly=None, xml=None, externalDocs=None, example=None, deprecated=None)

If you believe this was a mistake or this tool is missing a feature you need, please open an issue at https://github.com/openapi-generators/openapi-python-client/issues/new/choose

**Desktop (please complete the following information):**
 - OS: Ubuntu 25.04
 - Python Version: 3.12.3
 - openapi-python-client version: 0.28.0

Bắt đầu bằng cách chạy openapi-python-client generate --path=example.yaml --overwrite với hai schema trong issue, sau đó lần theo entry point của quá trình tạo model xử lý phần tử array inline và model được tham chiếu. Công việc được xem là hoàn tất khi dạng inline không còn báo cáo model ResultAThingsItem bị trùng lặp và response GET được giữ lại trong client được tạo.