fix(ajustes): show each settings row's current value

The prototype puts a trailing current-value string on nearly every
settings row (t4 lines 512-539, 625 -- "3 guardados", "Alfabetico",
"Espanol", "7 . 84 MB"). FilaAjuste only accepted icon/titulo/onTap,
so every row was value-blind.

Add an optional `valor` slot to FilaAjuste (13px, rgba(242,247,250,.55),
rendered before the chevron). Wire 8 of the 12 built rows to state
already available at the settings root: equalizer on/off, sleep-timer
active, favourite-group count, preferred station name, custom-station
count, sort order, recordings count-and-size (FutureBuilder over
EstadoGrabacion.listarGrabaciones), and the current language (hoisted
pantalla_ajustes_idioma.dart's native-name list to module level so the
root can read it without duplicating it). Salida de audio, Musica
local, Backup and Info's version are left without a value -- each
lacks a low-risk, deterministically-testable data source (see the
apply-progress note for the reason per row).

Reading EstadoRadio for these values through a root `context.watch`
would rebuild the whole settings list -- including the Grabaciones
FutureBuilder's disk read -- on every unrelated audio notification;
this follows the codebase's existing S4-R5 convention of narrow
`context.select` per field instead.

Ajustes' own PluriRootHeader/PluriScreenHeader edit (S2 in this same
pass) landed in this commit too, since both touched the same header
block in pantalla_ajustes.dart at the same time.

S8, Tier 1 visual-fidelity pass (audit id 2521).

lib/pantallas/ajustes/widgets/fila_ajuste.dart

@@ -17,7 +17,12 @@ class GrupoAjustes extends StatelessWidget {
   /// already in its display form — this style never applies `toUpperCase()`.
   final String titulo;
 
-  final List<FilaAjuste> filas;
+  /// S8 (Tier 1 visual fidelity): `Widget`, not `List<FilaAjuste>` — a few
+  /// rows source their current-value text asynchronously (e.g. recordings
+  /// count, app version) and wrap their own `FilaAjuste` in a
+  /// `FutureBuilder`. `GrupoAjustes` only iterates and inserts dividers; it
+  /// never reaches into `FilaAjuste`-specific state.
+  final List<Widget> filas;
 
   @override
   Widget build(BuildContext context) {
@@ -38,29 +43,54 @@ class GrupoAjustes extends StatelessWidget {
   }
 }
 
-/// A single Settings navigation row: icon, title, and a trailing chevron.
-/// Tapping it is the row's only behaviour — it carries no switches, sliders
-/// or text fields, which is what "zero inline controls" means at the root.
+/// A single Settings navigation row: icon, title, an optional trailing
+/// current-value string, and a trailing chevron. Tapping it is the row's
+/// only behaviour — it carries no switches, sliders or text fields, which
+/// is what "zero inline controls" means at the root.
 class FilaAjuste extends StatelessWidget {
   const FilaAjuste({
     super.key,
     required this.icon,
     required this.titulo,
     required this.onTap,
+    this.valor,
   });
 
   final IconData icon;
   final String titulo;
   final VoidCallback onTap;
 
+  /// S8 (Tier 1 visual fidelity): the prototype puts a trailing current
+  /// value on nearly every row (t4 lines 512-539, 625 — e.g. "3 guardados",
+  /// "Alfabético", "Español"), 13px `rgba(242,247,250,.55)`. Null means
+  /// "no current value to show" — the row renders exactly as before.
+  final String? valor;
+
   @override
   Widget build(BuildContext context) {
     final type = context.pluriType;
+    final valorActual = valor;
     return ListTile(
       contentPadding: EdgeInsets.zero,
       leading: Icon(icon),
       title: Text(titulo, style: type.cardTitle),
-      trailing: const Icon(Icons.chevron_right_rounded),
+      trailing: Row(
+        mainAxisSize: MainAxisSize.min,
+        children: [
+          if (valorActual != null) ...[
+            Text(
+              valorActual,
+              // bodyStrong is already 13/w600, matching the prototype's row
+              // value spec exactly — only the colour needs overriding.
+              style: type.bodyStrong.copyWith(
+                color: const Color(0xFFF2F7FA).withValues(alpha: 0.55),
+              ),
+            ),
+            const SizedBox(width: 6),
+          ],
+          const Icon(Icons.chevron_right_rounded),
+        ],
+      ),
       onTap: onTap,
     );
   }