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_zh.dart

@@ -717,6 +717,9 @@ class AppLocalizationsZh extends AppLocalizations {
   @override
   String get openFullPlayerTooltip => '打开完整播放器';
 
+  @override
+  String get nowListeningLabel => '正在收听';
+
   @override
   String get nothingPlayingTitle => '目前没有正在播放的内容';
 
@@ -755,6 +758,9 @@ class AppLocalizationsZh extends AppLocalizations {
   @override
   String get exploreNewSubtitle => '本周';
 
+  @override
+  String get popularNowTitle => '当前热门';
+
   @override
   String get offlineBannerTitle => '无连接';