fix(escuchar,reproductor): add the section-heading token and screen 1-3 polish

Audit S7 plus the open items on screens 1-3. Escuchar gains the
prototype's own 52px "now listening" eyebrow header (t4:53), which is
structurally different from the 56px title row every other root uses
(t4:325) -- the earlier wiring test asserted PluriRootHeader on all five
roots, an over-broad premise now corrected to guard what actually holds:
no AppBar, and the sleep-timer action still reachable.

lib/l10n/gen/app_localizations.dart

@@ -1402,6 +1402,12 @@ abstract class AppLocalizations {
   /// **'Abrir reproductor completo'**
   String get openFullPlayerTooltip;
 
+  /// No description provided for @nowListeningLabel.
+  ///
+  /// In es, this message translates to:
+  /// **'Escuchando ahora'**
+  String get nowListeningLabel;
+
   /// No description provided for @nothingPlayingTitle.
   ///
   /// In es, this message translates to:
@@ -1474,6 +1480,12 @@ abstract class AppLocalizations {
   /// **'Esta semana'**
   String get exploreNewSubtitle;
 
+  /// No description provided for @popularNowTitle.
+  ///
+  /// In es, this message translates to:
+  /// **'Populares ahora'**
+  String get popularNowTitle;
+
   /// No description provided for @offlineBannerTitle.
   ///
   /// In es, this message translates to: