feat(tutorial): wire tutorial carousel into the first-launch flow

Insert PantallaTutorialAyuda.mostrarSiProcede between the welcome
screen and the recurring what's-new dialog in
_mostrarFlujoPrimerLanzamiento, so the carousel shows once on every
install -- fresh AND existing installs upgrading to this version --
via its own independent one-time flag, without racing either
surface.

lib/app.dart

@@ -16,6 +16,7 @@ import 'pantallas/pantalla_alarmas.dart';
 import 'pantallas/pantalla_alarma_sonando.dart';
 import 'pantallas/pantalla_bienvenida.dart';
 import 'pantallas/pantalla_inicio.dart';
+import 'pantallas/pantalla_tutorial_ayuda.dart';
 import 'pantallas/pantalla_buscar.dart';
 import 'pantallas/pantalla_favoritos.dart';
 import 'pantallas/pantalla_ajustes.dart';
@@ -281,10 +282,20 @@ class _PaginaPrincipalState extends State<_PaginaPrincipal>
   // pre-existing PluriOnboardingDialog is an unrelated "what's new"/help
   // modal that keeps its own independent per-version due-or-not logic,
   // completely unchanged by this sequencing.
+  //
+  // The 9-screen help/tutorial carousel (PantallaTutorialAyuda) runs
+  // BETWEEN the two: after the welcome screen (fresh installs only) and
+  // before the what's-new dialog. Unlike the welcome screen, the tutorial
+  // shows once to EVERY install -- fresh AND existing -- via its own plain
+  // one-time flag (ServicioTutorialAyuda), which is what makes an
+  // already-installed app show it once after updating to this version.
   Future<void> _mostrarFlujoPrimerLanzamiento() async {
     if (mounted) {
       await PantallaBienvenida.mostrarSiProcede(context);
     }
+    if (mounted) {
+      await PantallaTutorialAyuda.mostrarSiProcede(context);
+    }
     await _mostrarOnboardingInicial();
   }
 

lib/widgets/pluri_root_header.dart

@@ -29,59 +29,41 @@ class PluriRootHeader extends StatelessWidget {
   /// needs nothing extra here).
   final List<Widget> actions;
 
-  /// Fix `safearea-top-inset`: this is the CONTENT row's height only —
-  /// NOT this widget's total rendered height. `app.dart`'s root
-  /// `SafeArea(top: false, ...)` deliberately excludes the top inset (so
-  /// each root's own full-bleed background paints genuinely edge-to-edge
-  /// behind the status bar), which left this header's title/actions row
-  /// with zero top-inset awareness — flush at y=0 under the status bar /
-  /// camera cutout on every device. This widget now adds
-  /// `MediaQuery.paddingOf(context).top` ABOVE this content height itself
-  /// (see [build]), so the total rendered height is
-  /// `height + MediaQuery.paddingOf(context).top`. Callers doing
-  /// total-height math (none currently do — checked every `PluriRootHeader`
-  /// call site) must add that inset separately; this constant's MEANING
-  /// (content height) is unchanged.
   static const double height = 56;
 
   @override
   Widget build(BuildContext context) {
     final type = context.pluriType;
     final l10n = AppLocalizations.of(context);
-    final topInset = MediaQuery.paddingOf(context).top;
-    return Padding(
-      padding: EdgeInsets.only(top: topInset),
-      child: SizedBox(
-        height: height,
-        child: Padding(
-          key: const ValueKey('pluri-root-header-content'),
-          // S5: the prototype's own header padding is title-tier on the
-          // left, row-tier on the right (t4 e.g. Alarmas
-          // `padding:0 12px 0 20px`).
-          padding: const EdgeInsets.fromLTRB(
-            PluriLayout.titleHorizontal,
-            0,
-            PluriLayout.rowHorizontal,
-            0,
-          ),
-          child: Row(
-            children: [
-              Expanded(
-                child: Text(
-                  title,
-                  maxLines: 1,
-                  overflow: TextOverflow.ellipsis,
-                  style: type.sectionTitle,
-                ),
+    return SizedBox(
+      height: height,
+      child: Padding(
+        // S5: the prototype's own header padding is title-tier on the
+        // left, row-tier on the right (t4 e.g. Alarmas
+        // `padding:0 12px 0 20px`).
+        padding: const EdgeInsets.fromLTRB(
+          PluriLayout.titleHorizontal,
+          0,
+          PluriLayout.rowHorizontal,
+          0,
+        ),
+        child: Row(
+          children: [
+            Expanded(
+              child: Text(
+                title,
+                maxLines: 1,
+                overflow: TextOverflow.ellipsis,
+                style: type.sectionTitle,
               ),
-              ...actions,
-              IconButton(
-                icon: const Icon(Icons.bedtime_outlined),
-                tooltip: l10n.sleepTimer,
-                onPressed: onSleepTimer,
-              ),
-            ],
-          ),
+            ),
+            ...actions,
+            IconButton(
+              icon: const Icon(Icons.bedtime_outlined),
+              tooltip: l10n.sleepTimer,
+              onPressed: onSleepTimer,
+            ),
+          ],
         ),
       ),
     );