feat(watch): clôture lot #91 - fréquence cardiaque live, notifications de séance et finitions montre

Consolide le lot applicatif watch companion validé :
- télémétrie fréquence cardiaque live remontée montre -> téléphone
  (collecteur watch, adapter Wear Data Layer, persistance Drift,
  propagation aux écrans historique/programme/profil/exécution)
- notifications de séance en arrière-plan côté téléphone (service
  foreground de statut + passerelle applicative)
- finitions montre : chrono d'étape, score d'étape, retrait du bouton
  "lancer une séance", thème, icônes et polices watch_app

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

lib/infrastructure/watch_bridge/native_watch_bridge_channel.dart

@@ -16,6 +16,10 @@ final class WatchBridgeConnectionEvent {
 abstract interface class WatchBridgeNativeChannel {
   Stream<WatchCommandEnvelope> get commands;
 
+  Stream<WatchSensorSummary> get sensorSummaries;
+
+  Stream<WatchSensorSample> get sensorSamples;
+
   Stream<WatchBridgeConnectionEvent> get connectionEvents;
 
   Future<void> publishProjection(WatchSessionProjection projection);
@@ -38,17 +42,31 @@ final class MethodChannelWatchBridgeNativeChannel
   const MethodChannelWatchBridgeNativeChannel({
     MethodChannel methodChannel = const MethodChannel(_methodChannelName),
     EventChannel commandChannel = const EventChannel(_commandChannelName),
+    EventChannel sensorSummaryChannel = const EventChannel(
+      _sensorSummaryChannelName,
+    ),
+    EventChannel sensorSampleChannel = const EventChannel(
+      _sensorSampleChannelName,
+    ),
     EventChannel connectionChannel = const EventChannel(_connectionChannelName),
   }) : _methodChannel = methodChannel,
        _commandChannel = commandChannel,
+       _sensorSummaryChannel = sensorSummaryChannel,
+       _sensorSampleChannel = sensorSampleChannel,
        _connectionChannel = connectionChannel;
 
   static const _methodChannelName = 'gametime.watch_bridge/methods';
   static const _commandChannelName = 'gametime.watch_bridge/commands';
+  static const _sensorSummaryChannelName =
+      'gametime.watch_bridge/sensor_summaries';
+  static const _sensorSampleChannelName =
+      'gametime.watch_bridge/sensor_samples';
   static const _connectionChannelName = 'gametime.watch_bridge/connection';
 
   final MethodChannel _methodChannel;
   final EventChannel _commandChannel;
+  final EventChannel _sensorSummaryChannel;
+  final EventChannel _sensorSampleChannel;
   final EventChannel _connectionChannel;
 
   @override
@@ -63,6 +81,30 @@ final class MethodChannelWatchBridgeNativeChannel
         });
   }
 
+  @override
+  Stream<WatchSensorSummary> get sensorSummaries {
+    return _sensorSummaryChannel
+        .receiveBroadcastStream()
+        .where((event) {
+          return event is Map;
+        })
+        .map((event) {
+          return WatchSensorSummary.fromJson(_stringObjectMap(event));
+        });
+  }
+
+  @override
+  Stream<WatchSensorSample> get sensorSamples {
+    return _sensorSampleChannel
+        .receiveBroadcastStream()
+        .where((event) {
+          return event is Map;
+        })
+        .map((event) {
+          return WatchSensorSample.fromJson(_stringObjectMap(event));
+        });
+  }
+
   @override
   Stream<WatchBridgeConnectionEvent> get connectionEvents {
     return _connectionChannel