Document and demonstrate native and layered configuration loading

layered.go

@@ -26,10 +26,13 @@ type LayeredOptions[T any] struct {
 	Overrides         []Override
 }
 
-// LoadLayered acquires the main input first, strictly composes each underlay,
-// then applies underlays in order beneath main, a selected overlay, and CLI
-// overrides. It performs defaults, decoding, resolution, and validation once.
-// Zero or one options value is accepted; any error returns a nil result.
+// LoadLayered acquires the main input first and strictly composes enabled
+// imports with each input's tier. It strictly composes contributions within
+// each underlay, then recursively combines underlays in listed order beneath
+// main, a selected overlay, and CLI overrides. Defaults, decoding, resolution,
+// and validation run once on the assembled input. Source IDs follow acquisition
+// order, not precedence order. Zero or one options value is accepted; any error
+// returns a nil result.
 func LoadLayered[T any](main Input, supplied ...LayeredOptions[T]) (*Result[T], error) {
 	options := make([]engine.LayeredOptions[T], len(supplied))
 	for index := range supplied {