Register (or clear) the resolver used to revive ClientDocument references
during defaultFromJSON. Called by the Foundry shim at module load so
the pure serialization core never imports Foundry directly.
Parameters
resolver: undefined|(uuid:string)=>unknown
A function mapping a document UUID to its live document, or
undefined to clear the registration.
Register (or clear) the resolver used to revive
ClientDocumentreferences during defaultFromJSON. Called by the Foundry shim at module load so the pure serialization core never imports Foundry directly.