Expose import defaults and selection evidence

layered.go

@@ -35,6 +35,9 @@ type Underlay struct{ Inputs []Input }
 type LayeredOptions[T any] struct {
 	Definition        Definition[T]
 	SourceVersionMode SourceVersionMode
+	// ImportDefaults supplies one load-wide default policy for enabled main,
+	// underlay, and transitive declarations. Explicit declaration values win.
+	ImportDefaults    ImportDefaults
 	Underlays         []Underlay
 	Overlay           string
 	OverlayFilesystem *FilesystemContext
@@ -73,6 +76,7 @@ func toEngineLayeredOptions[T any](options LayeredOptions[T]) engine.LayeredOpti
 		Overlay:           options.Overlay,
 		OverlayFilesystem: toEngineFilesystemContext(options.OverlayFilesystem),
 	}
+	result = engine.LayeredOptionsWithImportDefaults(result, toEngineImportDefaults(options.ImportDefaults))
 	if options.Underlays != nil {
 		result.Underlays = make([]engine.Underlay, len(options.Underlays))
 		for index, group := range options.Underlays {