feat(engine): add weekly goals with ISO-week rollover and +75 XP bonus

Phase 6 part 2b:
- solitaire_data::weekly defines WeeklyGoalKind, WeeklyGoalDef,
  WeeklyGoalContext, current_iso_week_key, and three starter goals
  (5 wins, 3 no-undo wins, 3 fast wins).
- PlayerProgress gains weekly_goal_week_iso, roll_weekly_goals_if_new_week,
  and record_weekly_progress (returns true exactly once per goal completion).
- WeeklyGoalsPlugin evaluates GameWonEvent against WEEKLY_GOALS, rolls the
  week if needed, increments matching counters, awards WEEKLY_GOAL_XP for
  newly-completed goals, persists progress, and fires
  WeeklyGoalCompletedEvent.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

solitaire_data/src/progress.rs

@@ -60,6 +60,11 @@ pub struct PlayerProgress {
     pub daily_challenge_last_completed: Option<NaiveDate>,
     pub daily_challenge_streak: u32,
     pub weekly_goal_progress: HashMap<String, u32>,
+    /// ISO week key (e.g. `"2026-W17"`) the current `weekly_goal_progress`
+    /// counters belong to. When the engine sees a different week it clears
+    /// progress and updates this field.
+    #[serde(default)]
+    pub weekly_goal_week_iso: Option<String>,
     pub unlocked_card_backs: Vec<usize>,
     pub unlocked_backgrounds: Vec<usize>,
     pub last_modified: DateTime<Utc>,
@@ -73,6 +78,7 @@ impl Default for PlayerProgress {
             daily_challenge_last_completed: None,
             daily_challenge_streak: 0,
             weekly_goal_progress: HashMap::new(),
+            weekly_goal_week_iso: None,
             unlocked_card_backs: vec![0],   // back #0 always available
             unlocked_backgrounds: vec![0],  // background #0 always available
             last_modified: DateTime::UNIX_EPOCH,
@@ -96,6 +102,32 @@ impl PlayerProgress {
         self.level > prev_level
     }
 
+    /// Reset weekly-goal progress when the ISO week has rolled over.
+    /// No-op if the stored week key already matches `current`.
+    pub fn roll_weekly_goals_if_new_week(&mut self, current: &str) -> bool {
+        if self.weekly_goal_week_iso.as_deref() == Some(current) {
+            return false;
+        }
+        self.weekly_goal_progress.clear();
+        self.weekly_goal_week_iso = Some(current.to_string());
+        self.last_modified = Utc::now();
+        true
+    }
+
+    /// Increment progress for `goal_id` by 1, capped at `target`.
+    /// Returns `true` if this call brought the counter from below `target`
+    /// to at-or-above `target` (i.e. just completed the goal).
+    pub fn record_weekly_progress(&mut self, goal_id: &str, target: u32) -> bool {
+        let entry = self.weekly_goal_progress.entry(goal_id.to_string()).or_insert(0);
+        if *entry >= target {
+            // Already complete — do not over-count.
+            return false;
+        }
+        *entry = entry.saturating_add(1);
+        self.last_modified = Utc::now();
+        *entry >= target
+    }
+
     /// Record a daily-challenge completion for `date`.
     ///
     /// - First completion ever, or a gap of more than one day: streak resets to 1.
@@ -323,6 +355,48 @@ mod tests {
         assert_eq!(p.daily_challenge_streak, 1);
     }
 
+    // --- Weekly goals ---
+
+    #[test]
+    fn first_week_roll_initializes_key_and_returns_true() {
+        let mut p = PlayerProgress::default();
+        let rolled = p.roll_weekly_goals_if_new_week("2026-W17");
+        assert!(rolled);
+        assert_eq!(p.weekly_goal_week_iso.as_deref(), Some("2026-W17"));
+    }
+
+    #[test]
+    fn same_week_roll_is_noop() {
+        let mut p = PlayerProgress::default();
+        p.roll_weekly_goals_if_new_week("2026-W17");
+        p.weekly_goal_progress.insert("g1".into(), 3);
+        let rolled = p.roll_weekly_goals_if_new_week("2026-W17");
+        assert!(!rolled);
+        assert_eq!(p.weekly_goal_progress.get("g1"), Some(&3));
+    }
+
+    #[test]
+    fn new_week_roll_clears_progress_and_updates_key() {
+        let mut p = PlayerProgress::default();
+        p.roll_weekly_goals_if_new_week("2026-W17");
+        p.weekly_goal_progress.insert("g1".into(), 3);
+        let rolled = p.roll_weekly_goals_if_new_week("2026-W18");
+        assert!(rolled);
+        assert!(p.weekly_goal_progress.is_empty());
+        assert_eq!(p.weekly_goal_week_iso.as_deref(), Some("2026-W18"));
+    }
+
+    #[test]
+    fn record_weekly_progress_returns_true_only_on_completion_step() {
+        let mut p = PlayerProgress::default();
+        assert!(!p.record_weekly_progress("g1", 3));
+        assert!(!p.record_weekly_progress("g1", 3));
+        assert!(p.record_weekly_progress("g1", 3), "third tick completes");
+        // Further ticks should not re-fire completion.
+        assert!(!p.record_weekly_progress("g1", 3));
+        assert_eq!(p.weekly_goal_progress.get("g1"), Some(&3));
+    }
+
     #[test]
     fn same_day_completion_is_idempotent() {
         let mut p = PlayerProgress::default();