feat(tokens): add design tokens, type scale, push scaffold, and root nav state

test/estado/estado_navegacion_test.dart

@@ -0,0 +1,75 @@
+import 'package:flutter_test/flutter_test.dart';
+import 'package:pluriwave/estado/estado_navegacion.dart';
+
+/// Design ADR-8: EstadoNavegacionRaiz is the single source of truth for
+/// which of the 5 root tabs is active. Switching roots never pushes a
+/// route — this is a plain ChangeNotifier update.
+void main() {
+  group('RaizPluriWave', () {
+    test('declaration order is the tab order (0-indexed)', () {
+      expect(RaizPluriWave.escuchar.index, 0);
+      expect(RaizPluriWave.buscar.index, 1);
+      expect(RaizPluriWave.favoritos.index, 2);
+      expect(RaizPluriWave.alarmas.index, 3);
+      expect(RaizPluriWave.ajustes.index, 4);
+      expect(RaizPluriWave.values.length, 5);
+    });
+  });
+
+  group('EstadoNavegacionRaiz', () {
+    test('starts on escuchar', () {
+      final estado = EstadoNavegacionRaiz();
+      expect(estado.actual, RaizPluriWave.escuchar);
+      expect(estado.indice, 0);
+    });
+
+    test('irA transitions to the requested root', () {
+      final estado = EstadoNavegacionRaiz();
+
+      estado.irA(RaizPluriWave.favoritos);
+
+      expect(estado.actual, RaizPluriWave.favoritos);
+    });
+
+    test('indice mirrors the enum declaration order after a transition', () {
+      final estado = EstadoNavegacionRaiz();
+
+      estado.irA(RaizPluriWave.alarmas);
+
+      expect(estado.indice, RaizPluriWave.alarmas.index);
+      expect(estado.indice, 3);
+    });
+
+    test('irA notifies listeners on a real transition', () {
+      final estado = EstadoNavegacionRaiz();
+      var notifyCount = 0;
+      estado.addListener(() => notifyCount++);
+
+      estado.irA(RaizPluriWave.buscar);
+
+      expect(notifyCount, 1);
+    });
+
+    test('irA no-ops and does not notify when already on that root', () {
+      final estado = EstadoNavegacionRaiz();
+      var notifyCount = 0;
+      estado.addListener(() => notifyCount++);
+
+      estado.irA(RaizPluriWave.escuchar); // already the starting root
+
+      expect(notifyCount, 0);
+      expect(estado.actual, RaizPluriWave.escuchar);
+    });
+
+    test('a repeated irA to the same non-initial root only notifies once', () {
+      final estado = EstadoNavegacionRaiz();
+      estado.irA(RaizPluriWave.ajustes);
+      var notifyCount = 0;
+      estado.addListener(() => notifyCount++);
+
+      estado.irA(RaizPluriWave.ajustes);
+
+      expect(notifyCount, 0);
+    });
+  });
+}