fix(escuchar): restore the prototype's 132px hero artwork

Audit 1.3: the hero art shipped at 84 where the prototype draws 132
(t4 line 56), with a 24 corner radius rather than the shared radiusMd.

Adds a dimension guard. Every existing test on this screen asserts
behaviour only, which is why an artwork 36% too small went unnoticed.

lib/pantallas/pantalla_inicio.dart

@@ -307,12 +307,15 @@ class _ArteEscuchar extends StatelessWidget {
 
   final Emisora emisora;
 
-  static const _lado = 84.0;
+  /// Audit 1.3: the prototype's Escuchar hero art is 132 (t4 line 56), and
+  /// its corner radius is 24 rather than the shared `radiusMd`.
+  static const _lado = 132.0;
+  static const _radio = 24.0;
 
   @override
   Widget build(BuildContext context) {
     final theme = Theme.of(context);
-    final radius = BorderRadius.circular(context.pluriTokens.radiusMd);
+    final radius = BorderRadius.circular(_radio);
     return PluriGlassSurface(
       padding: EdgeInsets.zero,
       borderRadius: radius,

lib/widgets/ecualizador_widget.dart

@@ -3,6 +3,7 @@ import 'package:flutter/material.dart';
 import '../l10n/gen/app_localizations.dart';
 import '../modelos/preset_ecualizador.dart';
 import '../tema/pluriwave_theme.dart';
+import '../tema/pluriwave_tokens.dart';
 import 'pluri_glass_surface.dart';
 
 class EcualizadorWidget extends StatefulWidget {
@@ -87,7 +88,9 @@ class _EcualizadorWidgetState extends State<EcualizadorWidget> {
                     child: Column(
                       children: [
                         SizedBox(
-                          height: 152,
+                          // Audit 11.4: the prototype draws the band column at
+                          // 280 (t4 line 581); 152 left the sliders 46% short.
+                          height: 280,
                           child: Semantics(
                             slider: true,
                             enabled: widget.habilitado,
@@ -100,13 +103,16 @@ class _EcualizadorWidgetState extends State<EcualizadorWidget> {
                               child: SliderTheme(
                                 data: SliderTheme.of(context).copyWith(
                                   trackHeight: 5,
-                                  activeTrackColor: tokens.liveGreen,
-                                  thumbColor: tokens.liveGreen,
+                                  // Audit 11.6: the prototype's band fill is
+                                  // brand teal (t4 line 585). `liveGreen` is
+                                  // the LIVE badge colour and reading it here
+                                  // put the sliders in the wrong colour family.
+                                  activeTrackColor: PluriWaveTokens.brand,
+                                  thumbColor: PluriWaveTokens.brand,
                                   inactiveTrackColor:
                                       theme.colorScheme.surfaceContainerHighest,
-                                  overlayColor: tokens.liveGreen.withValues(
-                                    alpha: 0.15,
-                                  ),
+                                  overlayColor: PluriWaveTokens.brand
+                                      .withValues(alpha: 0.15),
                                 ),
                                 child: Slider(
                                   value: _bandas[i],

test/pantallas/pantalla_inicio_test.dart

@@ -122,6 +122,48 @@ void main() {
       reason: 'switches tabs — must NOT push a new route',
     );
   });
+
+  testWidgets('visual fidelity (audit 1.3): the hero art is 132 square', (
+    tester,
+  ) async {
+    // The redesign shipped this at 84 — the prototype draws 132 (t4 line
+    // 56). Nothing caught it because every existing test here asserts
+    // behaviour, never dimensions. This is the guard that would have.
+    _setLargeSurfaceSize(tester);
+    final favoritos = FakeServicioFavoritos();
+    final estado = EstadoRadio(
+      audio: FakeServicioAudio(),
+      favoritos: favoritos,
+      radio: FakeServicioRadio(),
+      servicioEcualizador: FakeServicioEcualizador(),
+      servicioGrabacion: FakeServicioGrabacionRadio(),
+      resolverArchivoCustom: _archivoCustomVacio,
+      iniciarAutomaticamente: false,
+    );
+    addTearDown(estado.dispose);
+    await tester.runAsync(estado.inicializar);
+    final sonando = emisoraDemo(uuid: 'f1', nombre: 'Favorita Uno');
+    await favoritos.agregar(sonando);
+    await estado.cargarFavoritos();
+    // The hero only renders when a station is active — `emisoraActual` is
+    // what gates it. Without this the assertion below passes vacuously.
+    await tester.runAsync(() => estado.reproducir(sonando));
+
+    await tester.pumpWidget(
+      _conProviders(estado, _testApp(const PantallaInicio())),
+    );
+    await _pumpBounded(tester);
+
+    final cuadrados = tester
+        .widgetList<SizedBox>(find.byType(SizedBox))
+        .where((s) => s.width == 132 && s.height == 132);
+
+    expect(
+      cuadrados,
+      isNotEmpty,
+      reason: 'prototype t4 line 56 sizes the Escuchar hero artwork at 132',
+    );
+  });
 }
 
 /// Mirrors the app.dart wiring: EstadoRadio owns the domain notifiers and

test/widgets/ecualizador_widget_test.dart

@@ -2,6 +2,7 @@ import 'package:flutter/material.dart';
 import 'package:flutter_test/flutter_test.dart';
 import 'package:pluriwave/l10n/gen/app_localizations.dart';
 import 'package:pluriwave/modelos/preset_ecualizador.dart';
+import 'package:pluriwave/tema/pluriwave_tokens.dart';
 import 'package:pluriwave/widgets/ecualizador_widget.dart';
 
 /// WU13 task 13.1 — first-class regression guard (design ADR-5, spec
@@ -92,4 +93,47 @@ void main() {
       expect(slider.onChanged, isNotNull);
     }
   });
+
+  // Visual-fidelity guards (audit id 2521, items 11.4 and 11.6). These two
+  // values drifted silently once already: the whole point of the fidelity
+  // pass was that behavioural tests ("renders 5 sliders") never noticed the
+  // sliders were 46% too short and painted in the wrong colour family.
+  testWidgets('each band column is 280 tall, as the prototype draws it', (
+    tester,
+  ) async {
+    await tester.pumpWidget(buildWidget());
+
+    final columnas = tester.widgetList<SizedBox>(
+      find.descendant(
+        of: find.byType(EcualizadorWidget),
+        matching: find.byType(SizedBox),
+      ),
+    );
+
+    expect(
+      columnas.where((c) => c.height == 280),
+      hasLength(5),
+      reason:
+          'prototype t4 line 581 sizes the band column at 280; 152 left the '
+          'sliders 46% short',
+    );
+  });
+
+  testWidgets('band fill uses the brand teal, not the LIVE-badge green', (
+    tester,
+  ) async {
+    await tester.pumpWidget(buildWidget());
+
+    final tema = SliderTheme.of(tester.element(find.byType(Slider).first));
+
+    expect(tema.activeTrackColor, PluriWaveTokens.brand);
+    expect(tema.thumbColor, PluriWaveTokens.brand);
+    expect(
+      tema.activeTrackColor,
+      isNot(PluriWaveTokens.dark.liveGreen),
+      reason:
+          'liveGreen (#7EE4C2) is the LIVE badge colour; the prototype fills '
+          'EQ bands with brand teal #21D4D9 (t4 line 585)',
+    );
+  });
 }