fix(grabaciones): wire the recordings library into Settings navigation

WU15 shipped PantallaGrabaciones (the recordings library: storage bar,
recording rows, the "..." Rename/Share/Delete menu) fully tested but
reachable from nowhere in the app - a gap flagged in WU15's own
apply-progress notes, not fixed there since it needed a design
decision rather than a guess.

Coordinator ruling applied: the approved mockup's "Ajustes > Grabaciones"
screen depicts the library, not the folder/size settings form. So the
GRABACIONES Y MUSICA group's "Grabaciones" row in pantalla_ajustes.dart
now opens PantallaGrabaciones instead of PantallaAjustesGrabaciones.
The settings form is not dropped - it stays reachable, now from within
the library via a settings icon in its PluriPushScaffold actions,
matching the existing pantalla_ajustes_timer_sueno.dart "Add" action
precedent for a real capability living in the header.

One new ARB key (en/es only, per precedent): recordingsLibrarySettingsTooltip.

Tests: 604 -> 605 (one scenario re-targeted in pantalla_ajustes_test.dart,
one new scenario in pantalla_grabaciones_test.dart, which needed the
same ListTile-ink-assertion suppression helper WU3a/WU3b established
since it now pushes a ListTile-bearing settings screen). flutter
analyze unchanged at 1 pre-existing info.

Recorded in tasks.md as WU15b - not part of the original 18-unit plan,
added here to close the gap WU15 flagged.

test/pantallas/pantalla_ajustes_test.dart

@@ -246,23 +246,30 @@ void main() {
       },
     );
 
-    testWidgets('tapping the Grabaciones row pushes its detail screen', (
-      tester,
-    ) async {
-      setLargeSurface(tester);
-      _suppressListTileInkAssertion();
-      final estado = await crearEstado();
-      addTearDown(estado.dispose);
+    testWidgets(
+      'tapping the Grabaciones row pushes the recordings LIBRARY, not the '
+      'folder/size settings form (WU15b — the approved mockup screen '
+      '"Ajustes > Grabaciones" depicts the library)',
+      (tester) async {
+        setLargeSurface(tester);
+        _suppressListTileInkAssertion();
+        final estado = await crearEstado();
+        addTearDown(estado.dispose);
 
-      await tester.pumpWidget(buildAjustes(estado));
-      await pumpStable(tester);
+        await tester.pumpWidget(buildAjustes(estado));
+        await pumpStable(tester);
 
-      await tester.tap(find.text('Recordings'));
-      await pumpStable(tester);
+        await tester.tap(find.text('Recordings'));
+        await pumpStable(tester);
 
-      expect(find.byType(PluriPushScaffold), findsOneWidget);
-      expect(find.text('Change path'), findsOneWidget);
-    });
+        expect(find.byType(PluriPushScaffold), findsOneWidget);
+        expect(find.text('My recordings'), findsOneWidget);
+        // The folder/size settings form is reachable FROM the library now,
+        // not directly from the Settings root row — see
+        // pantalla_grabaciones_test.dart for that entry point.
+        expect(find.text('Change path'), findsNothing);
+      },
+    );
 
     testWidgets('tapping the Info row pushes its detail screen', (
       tester,

test/pantallas/pantalla_grabaciones_test.dart

@@ -24,6 +24,26 @@ import 'package:shared_preferences/shared_preferences.dart';
 /// the real `share_plus` call, since this suite does not mock that channel
 /// either (see `pantalla_ajustes_backup_test.dart`'s note on the same
 /// constraint).
+///
+/// Pre-existing project constraint (see `pantalla_ajustes_test.dart`):
+/// PluriGlassSurface paints a background over ListTile's ink layer, which
+/// Flutter flags as a warning-level assertion, not a correctness bug. Only
+/// needed by the WU15b settings-affordance test below, which pushes
+/// PantallaAjustesGrabaciones (a ListTile-with-onTap screen) — this file's
+/// other scenarios never mount that screen.
+void _suppressListTileInkAssertion() {
+  final original = FlutterError.onError;
+  FlutterError.onError = (details) {
+    if (details.exceptionAsString().contains(
+      'ListTile background color or ink splashes may be invisible',
+    )) {
+      return;
+    }
+    original?.call(details);
+  };
+  addTearDown(() => FlutterError.onError = original);
+}
+
 void main() {
   setUp(() {
     SharedPreferences.setMockInitialValues({});
@@ -95,6 +115,36 @@ void main() {
     expect(find.text('My recordings'), findsOneWidget);
   });
 
+  testWidgets(
+    'WU15b: tapping the settings icon pushes the folder/size settings '
+    'screen (PantallaAjustesGrabaciones stays reachable, now from within '
+    'the library instead of directly from the Settings root row)',
+    (tester) async {
+      _suppressListTileInkAssertion();
+      final estado = EstadoGrabacion(
+        servicio: _FakeServicioGrabacionConArchivos(
+          const [],
+          maxBytesFijo: 200 * 1024 * 1024,
+        ),
+      );
+      addTearDown(estado.dispose);
+
+      await tester.pumpWidget(
+        buildScreen(
+          estado: estado,
+          reproductor: _ReproductorGrabacionesFake(const {}),
+        ),
+      );
+      await pumpStable(tester);
+
+      await tester.tap(find.byIcon(Icons.settings_outlined));
+      await pumpStable(tester);
+
+      expect(find.byType(PluriPushScaffold), findsNWidgets(2));
+      expect(find.text('Change path'), findsOneWidget);
+    },
+  );
+
   testWidgets('15.1: storage bar reflects 84 of 200 MB used', (tester) async {
     final estado = EstadoGrabacion(
       servicio: _FakeServicioGrabacionConArchivos([