fix(timer): show the live countdown in the sleep timer sheet

showPluriSleepTimerSheet already had a working countdown branch
(ServicioTimer.tiempoRestanteStream), but every preset and the custom
duration flow popped the sheet immediately after starting the timer --
so the countdown never rendered in the primary flow, only if the user
happened to reopen the sheet afterwards.

Stop popping the sheet on start; the existing Consumer<EstadoRadio>
already reacts to iniciarTimerDuracion's notifyListeners and swaps to
the countdown view live. Also make the sheet scroll-controlled: at a
realistic phone width the countdown's title + description + headline-
sized remaining-time text overflowed the default half-screen cap that
never mattered while the sheet always closed before that view could
render.

lib/widgets/pluri_sleep_timer_sheet.dart

@@ -14,6 +14,13 @@ import 'pluri_layout.dart';
 void showPluriSleepTimerSheet(BuildContext context) {
   showModalBottomSheet(
     context: context,
+    // Issue 2 (feedback-pruebas): without this, the sheet is capped to a
+    // FRACTION of the screen height. That never mattered while the sheet
+    // always closed immediately after picking a duration (see the removed
+    // `Navigator.pop` calls below) -- now that the countdown view actually
+    // stays open, its title + description + headline-sized remaining-time
+    // text can overflow that capped height on a real phone width.
+    isScrollControlled: true,
     showDragHandle: true,
     builder:
         (ctx) => Consumer<EstadoRadio>(
@@ -79,12 +86,17 @@ void showPluriSleepTimerSheet(BuildContext context) {
                                     Duration(seconds: segundos),
                                   ),
                                 ),
-                                onPressed: () {
-                                  estado.iniciarTimerDuracion(
-                                    Duration(seconds: segundos),
-                                  );
-                                  Navigator.pop(ctx);
-                                },
+                                // Issue 2 (feedback-pruebas): no longer pops
+                                // the sheet -- `estado.iniciarTimerDuracion`
+                                // notifies this `Consumer<EstadoRadio>`,
+                                // which swaps straight to the countdown
+                                // view above so the user actually SEES the
+                                // remaining time instead of the sheet just
+                                // closing with no feedback.
+                                onPressed:
+                                    () => estado.iniciarTimerDuracion(
+                                      Duration(seconds: segundos),
+                                    ),
                               ),
                             ActionChip(
                               avatar: const Icon(Icons.tune_rounded, size: 18),
@@ -93,8 +105,9 @@ void showPluriSleepTimerSheet(BuildContext context) {
                                 final duracion =
                                     await _pedirDuracionPersonalizada(ctx);
                                 if (duracion == null || !ctx.mounted) return;
+                                // Issue 2: same as above -- stays open on
+                                // the countdown view rather than closing.
                                 estado.iniciarTimerDuracion(duracion);
-                                Navigator.pop(ctx);
                               },
                             ),
                           ],