[BUG] Schema generation fails when lowercase schema (item) is aliased to PascalCase (Item)

Bug Report Checklist

• Have you provided a full/minimal spec to reproduce the issue?
• Have you validated the input using an OpenAPI validator? (The spec is valid OAS 3.0)
• Have you tested with the latest master to confirm the issue still exists?
• Have you searched for related issues/PRs?
• What's the actual output vs expected output? (See Description below)
• [Optional] Sponsorship to speed up the bug fix or feature request (example)

Description

When generating a client, the model is not correctly created if the primary schema definition is in lowercase (item) but is referenced via a PascalCase alias (Item) which is then used in a path operation.

The generator fails to resolve the properties from the lowercase definition and skips the final Item model entirely, leading to TypeScript compilation errors when using TypeScript as a generator.

openapi-generator version

7.17.0

OpenAPI declaration file content or url

openapi: 3.0.0
info:
  title: "Case-Sensitive Alias Bug"
  version: 1.0.0

paths:
  /items:
    get:
      summary: Get an Item
      responses:
        '200':
          description: A single item object
          content:
            application/json:
              schema:
                $ref: "#/components/schemas/Item" # <-- References the PascalCase alias

components:
  schemas:
    # 1. Primary model definition (lowercase)
    item:
      type: object
      properties:
        id:
          type: string
        name:
          type: string
          
    # 2. Explicit alias (PascalCase) referencing the lowercase model
    Item:
      $ref: "#/components/schemas/item"

Generation Details

openapi-generator-cli generate -i schema.yaml -g typescript-axios

Steps to reproduce

1. Save the minimal OpenAPI specification above as schema.yaml.
2. Run the generation command using the typescript-axios generator.
3. Examine the generated model file for the Item interface.

Related issues/PRs

N/A

Start by running the minimal schema.yaml with the typescript-axios generator and inspect how the lowercase item definition and PascalCase Item alias are resolved. Compare the generated Item model and TypeScript compilation with the expected id and name properties; done means the aliased model is generated successfully without compilation errors.