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_en.dart

@@ -744,6 +744,9 @@ class AppLocalizationsEn extends AppLocalizations {
   @override
   String get openFullPlayerTooltip => 'Open full player';
 
+  @override
+  String get nowListeningLabel => 'Now listening';
+
   @override
   String get nothingPlayingTitle => 'Nothing playing yet';
 
@@ -783,6 +786,9 @@ class AppLocalizationsEn extends AppLocalizations {
   @override
   String get exploreNewSubtitle => 'This week';
 
+  @override
+  String get popularNowTitle => 'Popular now';
+
   @override
   String get offlineBannerTitle => 'No connection';