fix(favoritos): header actions row, chip colours

Audit 4.1 (t4:216): the manage-groups (create_new_folder) and sort
(swap_vert) actions now live in PluriRootHeader's own actions slot as
two icon buttons -- were an ActionChip inside the chip strip plus a
PopupMenuButton sharing a Row with it. The prototype's own back arrow
stays absent (binding decision: this root keeps its bottom tab bar,
unlike the prototype's pushed-with-back-arrow shape) -- this closes
the remaining gap in what was a partial fix.

Audit 4.2 (t4:219-221): group filter chips are solid brand teal with
dark text when active, listSurface + a faint border when not -- was
Material's own ChoiceChip theming (electricMagenta@24% selected).

Updated pantalla_favoritos_test.dart's two "Manage lists" text finders
to locate the relocated action by key instead (the action is now an
icon-only IconButton with a tooltip, not a labelled chip).

test/pantallas/pantalla_favoritos_test.dart

@@ -357,7 +357,12 @@ void main() {
       await tester.pumpWidget(buildScreen(estado));
       await pumpStable(tester);
 
-      await tester.tap(find.text('Manage lists'));
+      // Audit 4.1 (t4:216): the manage-groups action moved into the
+      // header as a create_new_folder icon button, replacing the old
+      // "Manage lists" ActionChip in the chip strip.
+      await tester.tap(
+        find.byKey(const ValueKey('favorites-manage-groups-action')),
+      );
       await pumpStable(tester);
 
       // "Group Management Reachable from Favoritos": the SAME screen
@@ -385,7 +390,10 @@ void main() {
       await tester.pumpAndSettle();
 
       expect(find.byType(PantallaAjustesGruposFavoritos), findsNothing);
-      expect(find.text('Manage lists'), findsOneWidget);
+      expect(
+        find.byKey(const ValueKey('favorites-manage-groups-action')),
+        findsOneWidget,
+      );
 
       await estado.crearGrupoFavoritos('Road trip');
       await pumpStable(tester);
@@ -494,6 +502,32 @@ void main() {
       },
     );
   });
+
+  group('visual fidelity (audit 4.2)', () {
+    testWidgets('the active group chip is solid brand teal with dark text; '
+        'inactive chips use listSurface (t4:219-221)', (tester) async {
+      setLargeSurface(tester);
+      _suppressListTileInkAssertion();
+      final estado = await crearEstadoConFavoritos();
+      addTearDown(estado.dispose);
+
+      await tester.pumpWidget(buildScreen(estado));
+      await pumpStable(tester);
+
+      final activo = tester.widget<ChoiceChip>(
+        find.widgetWithText(ChoiceChip, 'All · 3'),
+      );
+      expect(activo.selected, isTrue);
+      expect(activo.selectedColor, const Color(0xFF21D4D9));
+      expect(activo.labelStyle?.color, const Color(0xFF062126));
+
+      final inactivo = tester.widget<ChoiceChip>(
+        find.widgetWithText(ChoiceChip, 'Rock · 2'),
+      );
+      expect(inactivo.selected, isFalse);
+      expect(inactivo.backgroundColor, const Color(0xFF102532));
+    });
+  });
 }
 
 void setLargeSurface(WidgetTester tester) {