Collapses ~220 LOC of duplicated typed CRUD on AtprotoStore (Roaster, Grinder, Brewer) into thin wrappers over generic EntityCodec[M] helpers. Adds a ResolveRefs callback to entities.Descriptor so firehose no longer imports arabica types for feed-ref hydration; arabica's resolvers move to internal/entities/arabica/feed_refs.go.
Co-Authored-By: Claude Opus 4.7 (1M context) noreply@anthropic.com