fix: resolve union types using canonical type registry (swell 2.1.2)
When querying through forward join *Resolved fields, reverse joins like
socialGrainPhotoExifViaPhoto are now available on the resolved types.
The fix in swell 2.1.2 makes the executor use a canonical type registry
(built from introspection's deduplicated types) when resolving union types,
ensuring the most complete version of each type is used.
Adds test verifying Record union members have reverse join fields.