feat(engine): wire Stats Watch Replay button to in-engine playback

Promotes the Stats overlay's Watch Replay button from a stub
InfoToastEvent ("playback coming in a future build") to actually
starting in-engine playback via the new
replay_playback::start_replay_playback API. Pressing the button
when a replay exists resets the game to the recorded deal and the
ReplayOverlayPlugin's banner takes over.

The handler reads ReplayPlaybackState via Option<ResMut<...>> so
headless test fixtures that don't register ReplayPlaybackPlugin
keep compiling — they fall back to a descriptive "Replay ready"
toast. The "no replay yet" branch still surfaces the existing
"win a game first" toast.

Plugin registration in solitaire_app/src/main.rs picks up
ReplayPlaybackPlugin and ReplayOverlayPlugin alongside the existing
StatsPlugin. They run in any order — the playback plugin owns the
state resource, the overlay plugin spawns/despawns based on state
changes, and Stats's button handler dispatches into the playback
plugin's API.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

solitaire_app/src/main.rs

@@ -10,7 +10,8 @@ use solitaire_engine::{
     AudioPlugin, AutoCompletePlugin, CardAnimationPlugin, CardPlugin, ChallengePlugin,
     CursorPlugin, DailyChallengePlugin, FeedbackAnimPlugin, FontPlugin, GamePlugin, HelpPlugin,
     HomePlugin, HudPlugin, InputPlugin, LeaderboardPlugin, OnboardingPlugin, PausePlugin,
-    ProfilePlugin, ProgressPlugin, RadialMenuPlugin, SelectionPlugin, SettingsPlugin, SplashPlugin,
+    ProfilePlugin, ProgressPlugin, RadialMenuPlugin, ReplayOverlayPlugin, ReplayPlaybackPlugin,
+    SelectionPlugin, SettingsPlugin, SplashPlugin,
     StatsPlugin, SyncPlugin, TablePlugin, ThemePlugin, ThemeRegistryPlugin, TimeAttackPlugin,
     UiFocusPlugin, UiModalPlugin, UiTooltipPlugin, WeeklyGoalsPlugin, WinSummaryPlugin,
 };
@@ -117,6 +118,8 @@ fn main() {
         .add_plugins(FeedbackAnimPlugin)
         .add_plugins(CardAnimationPlugin)
         .add_plugins(AutoCompletePlugin)
+        .add_plugins(ReplayPlaybackPlugin)
+        .add_plugins(ReplayOverlayPlugin)
         .add_plugins(StatsPlugin::default())
         .add_plugins(ProgressPlugin::default())
         .add_plugins(AchievementPlugin::default())

solitaire_engine/src/stats_plugin.rs

@@ -187,27 +187,44 @@ fn refresh_latest_replay_on_win(
 
 /// Click handler for the "Watch replay" button.
 ///
-/// Replay playback lives on the sync server's web UI rather than in
-/// the desktop client. This handler currently surfaces a clear toast
-/// pointing the player there once the upload + URL is wired; until
-/// then it acknowledges the click and signals that the feature is on
-/// the way.
+/// Starts in-engine replay playback when the Watch Replay button is
+/// pressed. If no replay has been recorded yet, surfaces an
+/// [`InfoToastEvent`] instead. The playback path resets the live
+/// game to the recorded deal and ticks through the move list via
+/// [`crate::replay_playback`]; the [`crate::replay_overlay`] banner
+/// surfaces while playback runs.
 fn handle_watch_replay_button(
+    mut commands: Commands,
     buttons: Query<&Interaction, (With<WatchReplayButton>, Changed<Interaction>)>,
     latest: Res<LatestReplayResource>,
+    playback: Option<ResMut<crate::replay_playback::ReplayPlaybackState>>,
     mut toast: MessageWriter<InfoToastEvent>,
 ) {
     if !buttons.iter().any(|i| *i == Interaction::Pressed) {
         return;
     }
-    let message = match &latest.0 {
-        Some(replay) => format!(
-            "Replay ready ({}) \u{2014} web playback coming in a future build",
-            format_replay_caption(replay),
-        ),
-        None => "No replay recorded yet \u{2014} win a game first.".to_string(),
-    };
-    toast.write(InfoToastEvent(message));
+    match (&latest.0, playback) {
+        (Some(replay), Some(mut playback)) => {
+            crate::replay_playback::start_replay_playback(
+                &mut commands,
+                &mut playback,
+                replay.clone(),
+            );
+        }
+        (Some(replay), None) => {
+            // ReplayPlaybackPlugin not registered (headless test
+            // fixtures); fall back to a descriptive toast.
+            toast.write(InfoToastEvent(format!(
+                "Replay ready ({})",
+                format_replay_caption(replay)
+            )));
+        }
+        (None, _) => {
+            toast.write(InfoToastEvent(
+                "No replay recorded yet \u{2014} win a game first.".to_string(),
+            ));
+        }
+    }
 }
 
 /// Pure helper: render a one-line caption for a [`Replay`] suitable