fix(engine): reset weekly goals at app startup if the ISO week changed

evaluate_weekly_goals only ran the roll on GameWonEvent, so stale goal
progress from a prior week would linger until the player's next win.
A new Startup system calls roll_weekly_goals_if_new_week on launch and
persists immediately when the week has rolled over.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

solitaire_engine/src/weekly_goals_plugin.rs

@@ -27,6 +27,7 @@ impl Plugin for WeeklyGoalsPlugin {
     fn build(&self, app: &mut App) {
         app.add_event::<WeeklyGoalCompletedEvent>()
             .add_event::<GameWonEvent>()
+            .add_systems(Startup, roll_weekly_goals_on_startup)
             // Run after GameMutation (so GameWonEvent is available) and
             // ProgressUpdate (so we don't fight ProgressPlugin's add_xp).
             .add_systems(
@@ -38,6 +39,22 @@ impl Plugin for WeeklyGoalsPlugin {
     }
 }
 
+/// Rolls weekly-goal counters at startup so stale progress from a previous
+/// week never shows in the UI when the player launches the game.
+fn roll_weekly_goals_on_startup(
+    mut progress: ResMut<ProgressResource>,
+    path: Res<ProgressStoragePath>,
+) {
+    let week_key = current_iso_week_key(Local::now().date_naive());
+    if progress.0.roll_weekly_goals_if_new_week(&week_key) {
+        if let Some(target) = &path.0 {
+            if let Err(e) = save_progress_to(target, &progress.0) {
+                warn!("failed to save progress after weekly reset on startup: {e}");
+            }
+        }
+    }
+}
+
 fn evaluate_weekly_goals(
     mut wins: EventReader<GameWonEvent>,
     game: Res<GameStateResource>,
@@ -200,6 +217,35 @@ mod tests {
         assert!(fired.iter().any(|e| e.goal_id == "weekly_3_fast"));
     }
 
+    #[test]
+    fn stale_weekly_progress_is_cleared_on_startup() {
+        let mut app = headless_app();
+        // Inject progress from a past week.
+        {
+            let mut p = app.world_mut().resource_mut::<ProgressResource>();
+            p.0.weekly_goal_week_iso = Some("1970-W01".to_string());
+            p.0.weekly_goal_progress
+                .insert("weekly_5_wins".to_string(), 3);
+        }
+        // A second Startup run (re-init) is hard to trigger directly; instead
+        // call the helper through a fresh app that starts with stale data.
+        // Here we simulate the effect: roll_weekly_goals_if_new_week clears.
+        let current_week = current_iso_week_key(Local::now().date_naive());
+        let rolled = app
+            .world_mut()
+            .resource_mut::<ProgressResource>()
+            .0
+            .roll_weekly_goals_if_new_week(&current_week);
+        assert!(rolled, "expected stale week to trigger a roll");
+        assert!(
+            app.world()
+                .resource::<ProgressResource>()
+                .0
+                .weekly_goal_progress
+                .is_empty()
+        );
+    }
+
     #[test]
     fn weekly_goal_description_resolves_known_and_unknown() {
         assert_eq!(