Pass effective destinations through import traversal

internal/engine/destination.go

@@ -29,6 +29,13 @@ func normalizeDestination(path Path) (Path, error) {
 	return Path{segments: segments}, nil
 }
 
+// appendDestination combines validated mapping-key paths with owned segments.
+func appendDestination(parent, relative Path) Path {
+	segments := clonePathSegments(parent.segments, len(relative.segments))
+	segments = append(segments, relative.segments...)
+	return Path{segments: segments}
+}
+
 func invalidDestinationDiagnostic(destination Path) Diagnostic {
 	return Diagnostic{
 		Code: CodeOptionsInvalid, Severity: SeverityError,
@@ -37,12 +44,6 @@ func invalidDestinationDiagnostic(destination Path) Diagnostic {
 	}
 }
 
-func setSourceDestinations(sources []SourceInfo, destination Path) {
-	for index := range sources {
-		sources[index].Destination = destination.clone()
-	}
-}
-
 // placeDocument checks all per-document bounds before allocating destination
 // wrappers. Aggregate accounting remains the caller's responsibility.
 func placeDocument(body *document.Node, destination Path, sourceRoot document.Location, maxDepth, maxNodes int) (Path, *document.Node, error) {