feat(watch): renforce la vibration de fin de chrono et consolide la remontee des donnees stats montre

Cote montre pour #180 (vibration timerFinished plus longue et plus forte) et #179 (contrat/collecte des donnees stats vers le telephone).

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

watch_app/test/presentation/watch_session_screen_test.dart

@@ -347,6 +347,62 @@ void main() {
     },
   );
 
+  testWidgets(
+    'shows explicit metric states when sensor permission is required',
+    (tester) async {
+      final client = _FakeNativeWatchBridgeClient();
+      final viewModel = WatchSessionViewModel(nativeClient: client);
+
+      tester.view.devicePixelRatio = 1;
+      tester.view.physicalSize = const Size(192, 192);
+      addTearDown(tester.view.resetPhysicalSize);
+      addTearDown(tester.view.resetDevicePixelRatio);
+
+      await tester.pumpWidget(
+        MaterialApp(
+          theme: watchTheme(),
+          home: WatchSessionScreen(viewModel: viewModel),
+        ),
+      );
+
+      client.emitProjection(_runningProjection());
+      await tester.pump();
+      client.emitSensorSample(
+        WatchSensorSample(
+          sessionId: 'session-1',
+          capturedAtEpochMs: DateTime.utc(
+            2026,
+            7,
+            30,
+            10,
+          ).millisecondsSinceEpoch,
+          sensorCollectionStatus: 'authorizationRequired',
+        ),
+      );
+      await tester.pump();
+
+      expect(find.byTooltip('Stats'), findsOneWidget);
+
+      await tester.drag(
+        find.byKey(const ValueKey('watch-session-page')),
+        const Offset(-220, 0),
+      );
+      await tester.pumpAndSettle();
+      await tester.drag(
+        find.byKey(const ValueKey('watch-actions-page')),
+        const Offset(-220, 0),
+      );
+      await tester.pumpAndSettle();
+
+      expect(find.text('Stats'), findsOneWidget);
+      expect(find.text('Autorisation requise'), findsNWidgets(3));
+      expect(tester.takeException(), isNull);
+
+      await tester.pumpWidget(const SizedBox.shrink());
+      viewModel.dispose();
+    },
+  );
+
   testWidgets(
     'sends pause command from the icon button when a timer dominates',
     (tester) async {