OpenAPI script improvements (#3511)

- Improved detection of pagination objects
- Fix union type of duplicate inner types
- Deduplicated schemas in index
- Sort existing schemas when suggesting schemas with `--add`
- Support docstrings with content after schema list
- Handle special characters when creating Python property names
- Make `create class --tests` work with long class names
- Derive `--file` from long class name

Co-Authored-By: Claude <noreply@anthropic.com>