Expose input destinations through the public facade

layered.go

@@ -2,13 +2,17 @@ package configkit
 
 import "gitea.maximumdirect.net/eric/ConfigKit/internal/engine"
 
-// Input selects one source, whether its imports are enabled, and any explicit
-// filesystem context. A zero Source is invalid; use NoSource() for an omitted
-// main input. Sources keep their documented reuse and reader ownership rules.
+// Input selects one source, its application destination, whether its imports are
+// enabled, and any explicit filesystem context. A zero Source is invalid; use
+// NoSource() for an omitted main input. Sources keep their documented reuse and
+// reader ownership rules.
 type Input struct {
-	Source     Source
-	Imports    bool
-	Filesystem *FilesystemContext
+	Source Source
+	// Destination selects the mapping path where Source and its imported
+	// application contributions are placed. Its zero value keeps root placement.
+	Destination Path
+	Imports     bool
+	Filesystem  *FilesystemContext
 }
 
 // Underlay contains inputs that must compose strictly within one tier. Tiers
@@ -46,7 +50,7 @@ func LoadLayered[T any](main Input, supplied ...LayeredOptions[T]) (*Result[T],
 func toEngineInput(input Input) engine.Input {
 	return engine.Input{
 		Source: input.Source.toEngine(), Imports: input.Imports,
-		Filesystem: toEngineFilesystemContext(input.Filesystem),
+		Filesystem: toEngineFilesystemContext(input.Filesystem), Destination: toEnginePath(input.Destination),
 	}
 }