fix(auto): sort local-music subfolders before files

itemsLocales sorted a folder's children by name only, mixing directories
and files. A subfolder whose name sorted after enough tracks (e.g. "Live"
behind 80 numbered tracks) landed on a later "Más..." page, making it
unreachable without paging through every track first.

Sort directories before files, then by name within each group -- the
standard file-browser convention. Subfolders now always land on page 0.

lib/servicios/navegacion_auto.dart

@@ -30,6 +30,21 @@ List<T> paginaDe<T>(List<T> items, {required int pagina, required int tamano}) =
 bool hayPaginaSiguiente(int total, {required int pagina, required int tamano}) =>
     total > (pagina + 1) * tamano;
 
+/// Browse-tree ordering comparator for a local-music folder's children
+/// (Design "Directories before files", item 1): directories sort before
+/// files regardless of name, and within each group, alphabetically by
+/// [NodoLocal.nombre] -- the standard file-browser convention. Fixes a
+/// driver-facing bug where a folder's subfolders could land on a later
+/// "Más…" page whenever enough tracks sorted alphabetically ahead of them
+/// (e.g. a "Live" subfolder behind 80 numbered tracks), making the
+/// subfolder unreachable without paging through every track first.
+int compararNodoLocalParaNavegacion(NodoLocal a, NodoLocal b) {
+  if (a.esDirectorio != b.esDirectorio) {
+    return a.esDirectorio ? -1 : 1;
+  }
+  return a.nombre.compareTo(b.nombre);
+}
+
 const _prefijoEmisora = 'emisora:';
 
 /// Local-track media-id prefix (Design "media-id scheme"), collision-free
@@ -434,7 +449,7 @@ class ConstructorArbolAuto {
     MediaItem Function(NodoLocal, Map<String, MetadatosPista>)? construirItem,
   }) async {
     final construir = construirItem ?? _itemLocal;
-    final ordenados = [...nodos]..sort((a, b) => a.nombre.compareTo(b.nombre));
+    final ordenados = [...nodos]..sort(compararNodoLocalParaNavegacion);
     final paginaActual = paginaDe(ordenados, pagina: pagina, tamano: tamano);
     final docIds = paginaActual
         .where((n) => !n.esDirectorio)