Merge feature/gresiq-v1: GresIQ document-gateway SDK methods (ADR-0003 M2)

Adds upsert_document/get_collection to smbcloud-gresiq-sdk for the M2 dual-write path. Version bump to 0.4.7 is deferred to the uniform `make patch` release; docs (feature/gresiq-docs) merge only after publish.