Processes requested fields for Ash resources, determining which fields should be selected vs loaded, and building extraction templates for result processing.

This module handles different action types:

• CRUD actions (:read, :create, :update, :destroy) return resource records
• Generic actions (:action) return arbitrary types as specified in their returns field

Architecture

Delegates to FieldSelector, which uses a unified type-driven recursive dispatch pattern (similar to ValueFormatter). Each type is self-describing via {type, constraints}, so no separate classification step is needed.

Manifest module

Field selection needs lookups (resources, actions, types) that live on an AshTypescript.Manifest module's persisted Spark DSL state. process/4 accepts an optional manifest module — when omitted, defaults to the configured production manifest module. Verifiers running against an inline test manifest pass their own module.