fix(ecualizador): header switch, banner radius, preset chips, glow thumb

Audit 11.1 (t4:566): the master enable switch moves to
PluriPushScaffold's header actions -- was the body's first
SwitchListTile row. Its realtime/pending explainer subtitle stays
behind as a plain caption so no information is lost.

Audit 11.2 (t4:571): explainer banner radius is 16 (a local one-off,
matching neither of the 3 named tokens), not radiusSm's 14.

Audit 11.3 (t4:574-577): preset chips are solid brand-teal with dark
text when active, listSurface + a faint border when not -- was
Material's own ChoiceChip theming (primaryContainer/grey).

Audit 11.5 (t4:585): band sliders use a new 20x20 _GlowSliderThumbShape
(brand-teal blurred glow + solid thumb), replacing the Material
default round thumb.

Audit 11.7 (t4:584): the dB label is brand teal at 90% alpha, not
liveGreen -- a leftover wrong colour family 11.6's slider-only fix
never touched.

Updated 2 pre-existing tests (pantalla_ajustes_ecualizador_test.dart,
pantalla_ajustes_test.dart) to locate the enable switch by key instead
of by the "Enable equalizer" text it no longer renders next to.

lib/pantallas/ajustes/pantalla_ajustes_ecualizador.dart

@@ -8,6 +8,7 @@ import '../../estado/estado_radio.dart';
 import '../../l10n/gen/app_localizations.dart';
 import '../../modelos/preset_ecualizador.dart';
 import '../../tema/pluriwave_theme.dart';
+import '../../tema/pluriwave_tokens.dart';
 import '../../widgets/ecualizador_widget.dart';
 import '../../widgets/pluri_glass_surface.dart';
 import '../../widgets/pluri_layout.dart';
@@ -36,13 +37,33 @@ class PantallaAjustesEcualizador extends StatelessWidget {
   const PantallaAjustesEcualizador({super.key});
 
   @override
-  Widget build(BuildContext context) => PluriPushScaffold(
-    title: AppLocalizations.of(context).equalizerTitle,
-    body: ListView(
-      padding: PluriLayout.pageContentPadding,
-      children: const [_CuerpoEcualizador()],
-    ),
-  );
+  Widget build(BuildContext context) {
+    // Audit 11.1 (t4 line 566): the master enable switch lives in the
+    // HEADER, not as the body's first row -- read here (a second,
+    // cheap watch alongside _CuerpoEcualizadorState's own Consumer2)
+    // purely to feed PluriPushScaffold.actions.
+    final eq = context.watch<EstadoEcualizador>();
+    return PluriPushScaffold(
+      title: AppLocalizations.of(context).equalizerTitle,
+      actions: [
+        Padding(
+          padding: const EdgeInsets.only(right: 8),
+          child: Switch(
+            key: const ValueKey('eq-master-switch'),
+            value: eq.activo,
+            onChanged: eq.cambiarActivo,
+            // t4 line 569: brand-teal track, white thumb -- the default
+            // Material thumb colour already renders white when "on".
+            activeTrackColor: PluriWaveTokens.brand,
+          ),
+        ),
+      ],
+      body: ListView(
+        padding: PluriLayout.pageContentPadding,
+        children: const [_CuerpoEcualizador()],
+      ),
+    );
+  }
 }
 
 class _CuerpoEcualizador extends StatefulWidget {
@@ -83,17 +104,18 @@ class _CuerpoEcualizadorState extends State<_CuerpoEcualizador> {
         return Column(
           crossAxisAlignment: CrossAxisAlignment.stretch,
           children: [
-            SwitchListTile.adaptive(
-              contentPadding: EdgeInsets.zero,
-              title: Text(l10n.equalizerEnable),
-              subtitle: Text(
-                disponible
-                    ? l10n.equalizerRealtimeSubtitle
-                    : l10n.equalizerPendingSubtitle,
-              ),
-              value: eq.activo,
-              onChanged: eq.cambiarActivo,
+            // Audit 11.1 (t4 line 566): the enable switch itself now lives
+            // in PluriPushScaffold's header (see PantallaAjustesEcualizador
+            // above) -- this stays behind only as the explanatory caption
+            // the old SwitchListTile's subtitle carried, so that
+            // information is not lost.
+            Text(
+              disponible
+                  ? l10n.equalizerRealtimeSubtitle
+                  : l10n.equalizerPendingSubtitle,
+              style: Theme.of(ctx).textTheme.bodySmall,
             ),
+            const SizedBox(height: 12),
             if (mostrarModoPorEmisora) ...[
               const SizedBox(height: 8),
               SwitchListTile.adaptive(
@@ -164,6 +186,12 @@ class _BannerExplicacionBase extends StatelessWidget {
 
   final AppLocalizations l10n;
 
+  /// Audit 11.2 (t4 line 571): 16 -- doesn't match any of
+  /// [PluriWaveTokens]'s three named radii (14/18/30), so this stays a
+  /// local one-off constant (same precedent as `_stopButtonRadius` in
+  /// `pantalla_alarma_sonando.dart`).
+  static const _bannerRadius = 16.0;
+
   @override
   Widget build(BuildContext context) {
     final tokens = context.pluriTokens;
@@ -172,7 +200,7 @@ class _BannerExplicacionBase extends StatelessWidget {
       padding: const EdgeInsets.all(14),
       decoration: BoxDecoration(
         color: tokens.liveGreen.withValues(alpha: 0.09),
-        borderRadius: BorderRadius.circular(tokens.radiusSm),
+        borderRadius: BorderRadius.circular(_bannerRadius),
         border: Border.all(color: tokens.liveGreen.withValues(alpha: 0.26)),
       ),
       child: Row(