Generates TypeScript sort field as const arrays and derived union types for Ash resources.

Each resource gets:

• {resourceName}SortFields — a runtime as const array of sortable field names
• {ResourceName}SortField — a union type derived from the array

Sortable fields are driven by Ash.Info.Manifest: any field whose sortable? is true is included, formatted for the client (e.g. camelCase).