feat(engine): add daily challenge, level-up toast, and daily_devotee achievement

Phase 6 part 2 (partial):
- daily_seed_for(date) and PlayerProgress::record_daily_completion in
  solitaire_data, with streak logic that increments on consecutive days,
  resets on a skipped day, and is idempotent on same-day re-completions.
- DailyChallengePlugin tracks today's seed, awards +100 XP and updates
  the streak when the player wins a game whose seed matches. Pressing C
  starts a new game with the daily seed.
- LevelUpEvent toast in AnimationPlugin announces level changes.
- AchievementContext gains daily_challenge_streak; daily_devotee
  achievement unlocks at streak >= 7. AchievementPlugin reads
  ProgressResource and runs after ProgressUpdate.

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

solitaire_core/src/achievement.rs

@@ -20,6 +20,10 @@ pub struct AchievementContext {
     pub lifetime_score: u64,
     pub draw_three_wins: u32,
 
+    // Progression.
+    /// Current daily-challenge completion streak (consecutive days).
+    pub daily_challenge_streak: u32,
+
     // Last-win facts (GameWonEvent + GameState at win time).
     pub last_win_score: i32,
     pub last_win_time_seconds: u64,
@@ -96,6 +100,9 @@ fn early_bird(c: &AchievementContext) -> bool {
 fn speed_and_skill(c: &AchievementContext) -> bool {
     c.last_win_time_seconds < 90 && !c.last_win_used_undo
 }
+fn daily_devotee(c: &AchievementContext) -> bool {
+    c.daily_challenge_streak >= 7
+}
 
 /// All currently-evaluable achievements. Order is stable so persistence files
 /// remain readable across versions (new achievements append).
@@ -198,6 +205,13 @@ pub const ALL_ACHIEVEMENTS: &[AchievementDef] = &[
         secret: true,
         condition: speed_and_skill,
     },
+    AchievementDef {
+        id: "daily_devotee",
+        name: "Daily Devotee",
+        description: "Complete the daily challenge 7 days in a row",
+        secret: false,
+        condition: daily_devotee,
+    },
 ];
 
 /// Return every `AchievementDef` whose condition is satisfied by `ctx`.
@@ -225,6 +239,7 @@ mod tests {
             best_single_score: 0,
             lifetime_score: 0,
             draw_three_wins: 0,
+            daily_challenge_streak: 0,
             last_win_score: 0,
             last_win_time_seconds: u64::MAX,
             last_win_used_undo: true,
@@ -310,6 +325,18 @@ mod tests {
         assert!(!ids.contains(&"night_owl"));
     }
 
+    #[test]
+    fn daily_devotee_requires_7_day_streak() {
+        let mut c = ctx();
+        c.daily_challenge_streak = 6;
+        let ids: Vec<&str> = check_achievements(&c).iter().map(|d| d.id).collect();
+        assert!(!ids.contains(&"daily_devotee"));
+
+        c.daily_challenge_streak = 7;
+        let ids: Vec<&str> = check_achievements(&c).iter().map(|d| d.id).collect();
+        assert!(ids.contains(&"daily_devotee"));
+    }
+
     #[test]
     fn achievement_by_id_finds_known_and_returns_none_for_unknown() {
         assert_eq!(achievement_by_id("first_win").map(|d| d.name), Some("First Win"));