fix(visualizador): add a discrete-bar rendering mode

Audit 1.7/2.5 (t4 lines 66-68, 120-122): the prototype draws 30
discrete bottom-anchored bars (radius 2, vertical gradient); the
build's VisualizadorAudio painted a single continuous oscilloscope
stroke, so its `barras: 30` parameter never produced bars.

Adds an opt-in `barrasDiscretas` mode (default false, byte-identical
continuous rendering preserved for any other caller) plus a
`gradienteFinAlpha` knob for the two screens' differing gradient
end-alpha (.3 vs .45). Wires it into the Escuchar hero and the full
player, correcting the player's bar count/height to match the
prototype (26->30 bars, 46->40px) at the same time.

lib/pantallas/pantalla_inicio.dart

@@ -291,6 +291,9 @@ class _EscucharHero extends StatelessWidget {
                         barras: 30,
                         altura: 26,
                         color: context.pluriTokens.liveGreen,
+                        // Audit 1.7 (t4 lines 66-68): 30 discrete
+                        // bottom-anchored bars, not a continuous stroke.
+                        barrasDiscretas: true,
                       ),
                     ],
                   ),

lib/pantallas/pantalla_reproductor.dart

@@ -152,6 +152,7 @@ class _PantallaReproductorState extends State<PantallaReproductor> {
               ).pluriFadeIn(context, delay: const Duration(milliseconds: 230)),
               const SizedBox(height: 14),
               PluriGlassSurface(
+                key: const Key('player-visualizer'),
                 borderRadius: BorderRadius.circular(tokens.radiusLg),
                 padding: const EdgeInsets.symmetric(
                   horizontal: 14,
@@ -161,9 +162,13 @@ class _PantallaReproductorState extends State<PantallaReproductor> {
                   estadoStream: estado.estadoStream,
                   androidAudioSessionIdStream:
                       estado.audio.androidAudioSessionIdStream,
-                  barras: 26,
+                  // Audit 2.5 (t4 lines 120-122): 30 discrete bars at 40px,
+                  // gradient ending at 45% alpha (not the hero's 30%).
+                  barras: 30,
                   color: tokens.warmCoral,
-                  altura: 46,
+                  altura: 40,
+                  barrasDiscretas: true,
+                  gradienteFinAlpha: 0.45,
                 ),
               ).pluriFadeIn(context, delay: const Duration(milliseconds: 270)),
               const SizedBox(height: 22),

lib/widgets/visualizador_audio.dart

@@ -20,6 +20,18 @@ class VisualizadorAudio extends StatefulWidget {
   final double altura;
   final double anchuraTotal;
 
+  /// Audit 1.7/2.5 (t4 lines 66-68, 120-122): the prototype draws `barras`
+  /// discrete bottom-anchored bars (radius 2, vertical gradient), not a
+  /// continuous oscilloscope stroke. Defaults to `false` so every OTHER
+  /// caller (if any is ever added) keeps the original `_WaveFlowPainter`
+  /// rendering unchanged.
+  final bool barrasDiscretas;
+
+  /// Alpha of the gradient's BOTTOM colour stop in discrete-bar mode. The
+  /// two current consumers disagree (Escuchar hero: `.3`, t4 line 67; full
+  /// player: `.45`, t4 line 121), so this is a parameter, not a constant.
+  final double gradienteFinAlpha;
+
   const VisualizadorAudio({
     super.key,
     required this.estadoStream,
@@ -28,6 +40,8 @@ class VisualizadorAudio extends StatefulWidget {
     this.color,
     this.altura = 48,
     this.anchuraTotal = double.infinity,
+    this.barrasDiscretas = false,
+    this.gradienteFinAlpha = 0.3,
   });
 
   @override
@@ -184,12 +198,21 @@ class _VisualizadorAudioState extends State<VisualizadorAudio>
   @override
   Widget build(BuildContext context) {
     final color = widget.color ?? Theme.of(context).colorScheme.primary;
-    final t = _controller.value * pi * 2;
     return SizedBox(
       height: widget.altura,
       width: widget.anchuraTotal,
       child: RepaintBoundary(
-        child: CustomPaint(
+        child:
+            widget.barrasDiscretas
+                ? _construirBarrasDiscretas(color)
+                : _construirOnda(color),
+      ),
+    );
+  }
+
+  Widget _construirOnda(Color color) {
+    final t = _controller.value * pi * 2;
+    return CustomPaint(
       painter: _WaveFlowPainter(
         color: color,
         phase: t,
@@ -197,10 +220,57 @@ class _VisualizadorAudioState extends State<VisualizadorAudio>
         waveform: _ondaVisual,
       ),
       child: const SizedBox.expand(),
+    );
+  }
+
+  /// Audit 1.7/2.5 (t4 lines 66-68, 120-122): `barras` discrete,
+  /// bottom-anchored bars — radius 2, `gap:2px`, a top-to-bottom gradient
+  /// from [color] to `color@gradienteFinAlpha`. Reuses the SAME
+  /// `_ondaVisual`/`_ondaOrganica` amplitude source the continuous painter
+  /// already computes (real audio-session data when available, an organic
+  /// synthetic fallback otherwise) — only the paint strategy changes.
+  Widget _construirBarrasDiscretas(Color color) {
+    final valores = _valoresBarras();
+    final children = <Widget>[];
+    for (var i = 0; i < valores.length; i++) {
+      if (i > 0) children.add(const SizedBox(width: 2));
+      final valor = valores[i].clamp(0.08, 1.0);
+      children.add(
+        Expanded(
+          child: Align(
+            alignment: Alignment.bottomCenter,
+            child: Container(
+              key: ValueKey('visualizador-barra-$i'),
+              height: widget.altura * valor,
+              decoration: BoxDecoration(
+                borderRadius: BorderRadius.circular(2),
+                gradient: LinearGradient(
+                  begin: Alignment.topCenter,
+                  end: Alignment.bottomCenter,
+                  colors: [
+                    color,
+                    color.withValues(alpha: widget.gradienteFinAlpha),
+                  ],
+                ),
+              ),
+            ),
           ),
         ),
       );
     }
+    return Row(crossAxisAlignment: CrossAxisAlignment.end, children: children);
+  }
+
+  /// `_ondaVisual` is empty until the animation controller ticks at least
+  /// once (only happens once playback goes active, `_onEstado`'s
+  /// `_controller.repeat()`) — a discrete render before that must still show
+  /// `barras` resting bars, not zero, so it falls back to a flat, low
+  /// baseline of exactly [VisualizadorAudio.barras] values (clamped the same
+  /// way `_ondaOrganica` clamps its own count).
+  List<double> _valoresBarras() {
+    if (_ondaVisual.isNotEmpty) return _ondaVisual;
+    return List<double>.filled(widget.barras.clamp(8, 96), 0.12);
+  }
 }
 
 class _WaveFlowPainter extends CustomPainter {

test/pantallas/pantalla_inicio_test.dart

@@ -10,6 +10,7 @@ import 'package:pluriwave/estado/estado_radio.dart';
 import 'package:pluriwave/l10n/gen/app_localizations.dart';
 import 'package:pluriwave/modelos/emisora.dart';
 import 'package:pluriwave/pantallas/pantalla_inicio.dart';
+import 'package:pluriwave/widgets/visualizador_audio.dart';
 import 'package:provider/provider.dart';
 import 'package:shared_preferences/shared_preferences.dart';
 
@@ -208,6 +209,51 @@ void main() {
     );
   });
 
+  testWidgets(
+    'visual fidelity (audit 1.7): the hero visualizer renders 30 discrete '
+    'bars, not the continuous waveform stroke',
+    (tester) async {
+      // Item 16 is exactly the widget the audit warned about
+      // (visualizador_audio.dart:77, `_controller.repeat()`) — bounded pump
+      // only, never pumpAndSettle.
+      _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();
+      await tester.runAsync(() => estado.reproducir(sonando));
+
+      await tester.pumpWidget(
+        _conProviders(estado, _testApp(const PantallaInicio())),
+      );
+      await _pumpBounded(tester);
+
+      expect(
+        find.byKey(const Key('visualizador-barra-0')),
+        findsOneWidget,
+        reason: 'prototype t4 line 66-68: 30 discrete bottom-anchored bars',
+      );
+      expect(
+        find.descendant(
+          of: find.byType(VisualizadorAudio),
+          matching: find.byType(CustomPaint),
+        ),
+        findsNothing,
+      );
+    },
+  );
+
   testWidgets(
     'visual fidelity (audit 1.6): a station missing every meta field omits '
     'the line gracefully, no stray separators',

test/pantallas/pantalla_reproductor_test.dart

@@ -412,6 +412,35 @@ void main() {
         },
       );
 
+      testWidgets(
+        'visual fidelity (audit 2.5): the visualizer renders 30 discrete '
+        'bars, not the continuous waveform stroke',
+        (tester) async {
+          final estado = crearEstado();
+          addTearDown(estado.dispose);
+
+          await montarPantalla(tester, estado);
+
+          final visualizador = find.byKey(const Key('player-visualizer'));
+          expect(visualizador, findsOneWidget);
+          expect(
+            find.descendant(
+              of: visualizador,
+              matching: find.byKey(const Key('visualizador-barra-0')),
+            ),
+            findsOneWidget,
+            reason: 'prototype t4 line 120-122: 30 discrete bars',
+          );
+          expect(
+            find.descendant(
+              of: visualizador,
+              matching: find.byType(CustomPaint),
+            ),
+            findsNothing,
+          );
+        },
+      );
+
       testWidgets(
         'exactly 4 tool-tray tiles render: EQ propio, Grabar, sleep timer, Compartir',
         (tester) async {

test/widgets/visualizador_audio_barras_test.dart

@@ -0,0 +1,153 @@
+import 'dart:async';
+
+import 'package:flutter/material.dart';
+import 'package:flutter_test/flutter_test.dart';
+import 'package:pluriwave/servicios/servicio_audio.dart';
+import 'package:pluriwave/widgets/visualizador_audio.dart';
+
+/// Audit 1.7/2.5 (t4 lines 66-68, 120-122): the prototype draws 30 discrete
+/// bottom-anchored bars (`border-radius:2px`, a top-to-bottom gradient), but
+/// `_WaveFlowPainter` (`visualizador_audio.dart:206-275`) paints a single
+/// continuous oscilloscope stroke — the `barras` parameter was inert. These
+/// guards assert the actual bar COUNT and that the render is structurally
+/// discrete (no `CustomPaint` stroke), not just "looks bar-ish".
+void main() {
+  group('VisualizadorAudio.barrasDiscretas', () {
+    testWidgets(
+      'renders exactly `barras` discrete bars, not a single CustomPaint path',
+      (tester) async {
+        final controller = StreamController<EstadoReproduccion>.broadcast();
+        addTearDown(controller.close);
+
+        await tester.pumpWidget(
+          MaterialApp(
+            home: Scaffold(
+              body: VisualizadorAudio(
+                estadoStream: controller.stream,
+                barras: 30,
+                barrasDiscretas: true,
+              ),
+            ),
+          ),
+        );
+        await tester.pump();
+
+        for (var i = 0; i < 30; i++) {
+          expect(
+            find.byKey(Key('visualizador-barra-$i')),
+            findsOneWidget,
+            reason: 'bar $i of 30 must exist (t4 lines 66-68: 30 bars)',
+          );
+        }
+        expect(
+          find.byKey(const Key('visualizador-barra-30')),
+          findsNothing,
+          reason: 'exactly 30 bars, not 31+',
+        );
+        expect(
+          find.descendant(
+            of: find.byType(VisualizadorAudio),
+            matching: find.byType(CustomPaint),
+          ),
+          findsNothing,
+          reason:
+              'discrete mode must not fall back to the continuous '
+              '_WaveFlowPainter stroke',
+        );
+      },
+    );
+
+    testWidgets('each bar has radius 2 and a top-to-bottom gradient ending '
+        'at the given alpha (t4 line 67: linear-gradient(180deg,#7EE4C2,'
+        'rgba(126,228,194,.3)))', (tester) async {
+      final controller = StreamController<EstadoReproduccion>.broadcast();
+      addTearDown(controller.close);
+      const color = Color(0xFF7EE4C2);
+
+      await tester.pumpWidget(
+        MaterialApp(
+          home: Scaffold(
+            body: VisualizadorAudio(
+              estadoStream: controller.stream,
+              barras: 8,
+              barrasDiscretas: true,
+              color: color,
+            ),
+          ),
+        ),
+      );
+      await tester.pump();
+
+      final barra = tester.widget<Container>(
+        find.byKey(const Key('visualizador-barra-0')),
+      );
+      final decoracion = barra.decoration as BoxDecoration;
+      expect(
+        decoracion.borderRadius,
+        BorderRadius.circular(2),
+        reason: 't4 line 67: border-radius:2px',
+      );
+      final gradiente = decoracion.gradient as LinearGradient;
+      expect(gradiente.begin, Alignment.topCenter);
+      expect(gradiente.end, Alignment.bottomCenter);
+      expect(gradiente.colors.first, color);
+      expect(gradiente.colors.last, color.withValues(alpha: 0.3));
+    });
+
+    testWidgets(
+      'a custom gradienteFinAlpha changes only the gradient END colour '
+      '(t4 line 121: the player uses rgba(244,184,96,.45), not .3)',
+      (tester) async {
+        final controller = StreamController<EstadoReproduccion>.broadcast();
+        addTearDown(controller.close);
+        const color = Color(0xFFF4B860);
+
+        await tester.pumpWidget(
+          MaterialApp(
+            home: Scaffold(
+              body: VisualizadorAudio(
+                estadoStream: controller.stream,
+                barras: 8,
+                barrasDiscretas: true,
+                color: color,
+                gradienteFinAlpha: 0.45,
+              ),
+            ),
+          ),
+        );
+        await tester.pump();
+
+        final barra = tester.widget<Container>(
+          find.byKey(const Key('visualizador-barra-0')),
+        );
+        final gradiente =
+            (barra.decoration as BoxDecoration).gradient as LinearGradient;
+        expect(gradiente.colors.last, color.withValues(alpha: 0.45));
+      },
+    );
+
+    testWidgets('barrasDiscretas defaults to false — existing callers keep the '
+        'continuous CustomPaint stroke, no regression', (tester) async {
+      final controller = StreamController<EstadoReproduccion>.broadcast();
+      addTearDown(controller.close);
+
+      await tester.pumpWidget(
+        MaterialApp(
+          home: Scaffold(
+            body: VisualizadorAudio(estadoStream: controller.stream),
+          ),
+        ),
+      );
+      await tester.pump();
+
+      expect(
+        find.descendant(
+          of: find.byType(VisualizadorAudio),
+          matching: find.byType(CustomPaint),
+        ),
+        findsOneWidget,
+      );
+      expect(find.byKey(const Key('visualizador-barra-0')), findsNothing);
+    });
+  });
+}