fix: resolve OpenAPI validation errors in JsonPatchOperation schema
- Fix .redocly.yaml configuration: change 'warning' to 'warn' for valid severity levels
- Remove invalid 'info-description' and 'license-url' rules from Redocly config
- Refactor JsonPatchOperation schema to use oneOf instead of if/then/else
- Add explicit type definitions for all operation variants (add/replace/test, move/copy, remove)
- Resolve 'no-required-schema-properties-undefined' linting errors
This fixes the pipeline validation failures in test:green-phase.