fix(radio): treat custom-station path resolution as part of the IO surface

_cargarEmisorasCustom resolved the file path outside the IO guard, so
a throw from the resolver escaped into _init()'s Future.wait and took
the sibling loads (populares, favoritos, grupos) down with it — a gap
the old catch-all used to cover. Path resolution now gets the same
IO-fail treatment as an unreadable file: degraded flag, logged skip,
siblings unaffected.

test/estado/estado_radio_test.dart

@@ -408,6 +408,30 @@ void main() {
         },
       );
 
+      test(
+        'si resolver la ruta del archivo custom falla, la inicializacion '
+        'sobrevive y las cargas hermanas no se pierden (D5 IO-fail)',
+        () async {
+          final estado = EstadoRadio(
+            audio: FakeServicioAudio(),
+            favoritos: FakeServicioFavoritos(),
+            radio: FakeServicioRadio(),
+            servicioEcualizador: FakeServicioEcualizador(),
+            resolverArchivoCustom:
+                () async => throw const FileSystemException('sin storage'),
+            iniciarAutomaticamente: false,
+          );
+
+          // Path resolution failing must be treated as an IO-fail, not
+          // escape _cargarEmisorasCustom: it runs inside _init()'s
+          // Future.wait, so an uncaught throw would also reject the
+          // sibling loads (populares/favoritos/grupos).
+          await estado.inicializar();
+
+          expect(estado.emisorasCustom, isEmpty);
+        },
+      );
+
       test(
         'JSON invalido al nivel superior pone en cuarentena el archivo '
         'original (D5 parse-fail)',