Generator fails with non-specific error instead of saying it doesn't support the version of OAS

Description

I have an OpenAPI 3.1 API definition, which I converted from YAML to JSON because of https://github.com/OpenAPITools/openapi-generator/issues/9520

Attempting to generate any code with it fails, with only:
Exception in thread "main" java.lang.RuntimeException: Issues with the OpenAPI input. Possible causes: invalid/missing spec, malformed JSON/YAML files, etc.

openapi-generator version

6.0.1

OpenAPI declaration file content or url

{
  "openapi": "3.1.0",
  "info": {
    "version": "1.0.0",
    "title": "MediaDevice API",
...
}

Generation Details

The command I used:
openapi-generator-cli generate -i deviceAPI.json -g nodejs-express-server -o ~/node_server

Steps to reproduce

Try to generate code from any OAS 3.1 document (JSON currently because YAML is broken).

Suggest a fix

Raise an error message saying that the version of OAS is not supported by the generator.

Start by reproducing the openapi-generator-cli generate command with the supplied deviceAPI.json containing openapi: 3.1.0, then trace the generator's input-validation error path. Done means an unsupported OAS version produces a specific error instead of the generic input failure, with regression coverage for this case.