#3497 refactor: Fixed the type annotation for the `refs` attribute of the `singer_sdk.singerlib.resolve_schema_references` function Pull request opened by edgarrmondragon ## Summary by Sourcery Refine JSON schema typing by introducing a shared schema dictionary alias and correcting the type annotations for schema serialization and reference resolution helpers. Enhancements: • Introduce a _SchemaDict type alias to represent JSON schema dictionaries consistently across the module. • Correct the type annotations of resolve_schema_references and its helper to use structured schema and reference mappings instead of loosely typed dicts. meltano/sdk