feat(ads): rewarded ad gates the continue/extra-moves rescue

lib/ui/screens/game_screen.dart

@@ -117,6 +117,7 @@ class _GameScreenState extends ConsumerState<GameScreen>
 
   void _onSessionChange(GameViewState? prev, GameViewState? next) {
     if (next == null) return;
+    if (prev == null) ref.read(adServiceProvider).onRoundStart();
     final audio = ref.read(audioServiceProvider);
     if (prev?.fxTick != next.fxTick && next.lastPlacement != null) {
       final placement = next.lastPlacement!;
@@ -153,6 +154,9 @@ class _GameScreenState extends ConsumerState<GameScreen>
       if (next.phase != GamePhase.playing) {
         ref.read(tutorialProvider.notifier).skip();
       }
+      if (next.phase == GamePhase.won || next.phase == GamePhase.lost) {
+        ref.read(adServiceProvider).onStageCompleted();
+      }
       if (next.phase == GamePhase.won) {
         audio.play(Sfx.win);
         // recordResult keeps the best run, so re-entry is harmless.
@@ -393,7 +397,10 @@ class _GameScreenState extends ConsumerState<GameScreen>
           [
             if (!view.rescueUsed)
               FilledButton(
-                onPressed: () {
+                onPressed: () async {
+                  final earned =
+                      await ref.read(adServiceProvider).showRewarded();
+                  if (!earned) return;
                   ref.read(analyticsProvider).rescueUsed(type: 'extra_moves');
                   notifier.addExtraMoves();
                 },
@@ -416,7 +423,10 @@ class _GameScreenState extends ConsumerState<GameScreen>
           [
             if (!view.rescueUsed)
               FilledButton(
-                onPressed: () {
+                onPressed: () async {
+                  final earned =
+                      await ref.read(adServiceProvider).showRewarded();
+                  if (!earned) return;
                   ref.read(analyticsProvider).rescueUsed(type: 'continue');
                   notifier.useContinue();
                 },