feat(data,sync,engine): per-mode best score and fastest win

Lifetime stats now also track best score and fastest win per game
mode (Classic, Zen, Challenge), additive on top of the existing
all-modes-combined `best_single_score` and `fastest_win_seconds`.
Time Attack is intentionally excluded — its scoring model is
session-level (count of wins inside a 10-minute window) so a
per-game best wouldn't compose. Daily Challenge inherits Classic
scoring and contributes through the Classic row.

- `solitaire_sync::StatsSnapshot` gains six fields (`{mode}_best_score`,
  `{mode}_fastest_win_seconds` × {Classic, Zen, Challenge}). All are
  `#[serde(default)]` so older save files load cleanly to zeros.
- `solitaire_sync::merge` propagates the per-mode bests through the
  same max/min logic as the global counterparts.
- `solitaire_data::StatsExt::update_per_mode_bests` is the engine's
  entry point — called from `update_stats_on_win` alongside the
  existing `update_on_win`.
- Stats overlay grows a "Per-mode bests" section with three rows
  (Classic / Zen / Challenge) tagged with `PerModeBestsRow`. Empty
  rows render an em-dash, matching the first-launch zero-state
  treatment used by the primary cells.
- 3 new tests cover the rendering, the Classic-mode update path,
  and the Zen-mode update path.

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

solitaire_data/src/stats.rs

@@ -5,16 +5,35 @@
 //! `update_on_win` method that depends on [`DrawMode`] from `solitaire_core`.
 
 use chrono::Utc;
-use solitaire_core::game_state::DrawMode;
+use solitaire_core::game_state::{DrawMode, GameMode};
 
 pub use solitaire_sync::StatsSnapshot;
 
 /// Extension trait providing game-logic mutation helpers for [`StatsSnapshot`].
 ///
-/// Import this trait alongside `StatsSnapshot` to use `update_on_win`.
+/// Import this trait alongside `StatsSnapshot` to use `update_on_win`
+/// and [`StatsExt::update_per_mode_bests`].
 pub trait StatsExt {
     /// Updates rolling statistics from a completed game win. Call once per `GameWonEvent`.
+    ///
+    /// Tracks lifetime totals only — per-mode best scores and times are
+    /// updated separately via [`StatsExt::update_per_mode_bests`] so the
+    /// long-standing call sites that only know about [`DrawMode`] keep
+    /// compiling.
     fn update_on_win(&mut self, score: i32, time_seconds: u64, draw_mode: &DrawMode);
+
+    /// Updates the per-mode best score and fastest-win-time fields for the
+    /// given [`GameMode`]. Call alongside [`StatsExt::update_on_win`] from
+    /// the win handler.
+    ///
+    /// Behaviour:
+    /// - `Classic`, `Zen`, `Challenge`: updates the matching `*_best_score`
+    ///   (max) and `*_fastest_win_seconds` (zero-aware min — 0 means
+    ///   "no win recorded yet").
+    /// - `TimeAttack`: no-op. Time Attack uses session-level scoring (count
+    ///   of wins in 10 minutes); a per-game best wouldn't compose with
+    ///   the other modes' single-game scoring.
+    fn update_per_mode_bests(&mut self, score: i32, time_seconds: u64, mode: GameMode);
 }
 
 impl StatsExt for StatsSnapshot {
@@ -51,6 +70,43 @@ impl StatsExt for StatsSnapshot {
 
         self.last_modified = Utc::now();
     }
+
+    fn update_per_mode_bests(&mut self, score: i32, time_seconds: u64, mode: GameMode) {
+        let score_u32 = score.max(0) as u32;
+        // Zero-aware min — 0 means "no win recorded yet" for the per-mode
+        // fastest fields, so we must not let a real time get clobbered to 0.
+        // (Mirrors the merge logic in `solitaire_sync::merge`.)
+        let min_ignore_zero = |existing: u64, candidate: u64| -> u64 {
+            if existing == 0 {
+                candidate
+            } else if candidate == 0 {
+                existing
+            } else {
+                existing.min(candidate)
+            }
+        };
+        match mode {
+            GameMode::Classic => {
+                self.classic_best_score = self.classic_best_score.max(score_u32);
+                self.classic_fastest_win_seconds =
+                    min_ignore_zero(self.classic_fastest_win_seconds, time_seconds);
+            }
+            GameMode::Zen => {
+                self.zen_best_score = self.zen_best_score.max(score_u32);
+                self.zen_fastest_win_seconds =
+                    min_ignore_zero(self.zen_fastest_win_seconds, time_seconds);
+            }
+            GameMode::Challenge => {
+                self.challenge_best_score = self.challenge_best_score.max(score_u32);
+                self.challenge_fastest_win_seconds =
+                    min_ignore_zero(self.challenge_fastest_win_seconds, time_seconds);
+            }
+            // Time Attack uses its own session-level scoring; a per-game best
+            // wouldn't compose with the other modes' single-game numbers.
+            GameMode::TimeAttack => {}
+        }
+        self.last_modified = Utc::now();
+    }
 }
 
 #[cfg(test)]
@@ -177,4 +233,123 @@ mod tests {
         s.update_on_win(200, 60, &DrawMode::DrawOne);
         assert_eq!(s.lifetime_score, u64::MAX, "lifetime_score must saturate, not overflow");
     }
+
+    // -----------------------------------------------------------------------
+    // Per-mode bests
+    // -----------------------------------------------------------------------
+
+    #[test]
+    fn classic_win_updates_classic_best_score_only() {
+        let mut s = StatsSnapshot::default();
+        s.update_per_mode_bests(1500, 200, GameMode::Classic);
+        assert_eq!(s.classic_best_score, 1500);
+        assert_eq!(s.classic_fastest_win_seconds, 200);
+        // Other modes untouched.
+        assert_eq!(s.zen_best_score, 0);
+        assert_eq!(s.zen_fastest_win_seconds, 0);
+        assert_eq!(s.challenge_best_score, 0);
+        assert_eq!(s.challenge_fastest_win_seconds, 0);
+    }
+
+    #[test]
+    fn zen_win_updates_zen_best_score_only() {
+        let mut s = StatsSnapshot::default();
+        s.update_per_mode_bests(1800, 600, GameMode::Zen);
+        assert_eq!(s.zen_best_score, 1800);
+        assert_eq!(s.zen_fastest_win_seconds, 600);
+        assert_eq!(s.classic_best_score, 0);
+        assert_eq!(s.challenge_best_score, 0);
+    }
+
+    #[test]
+    fn challenge_win_updates_challenge_best_score_only() {
+        let mut s = StatsSnapshot::default();
+        s.update_per_mode_bests(2400, 480, GameMode::Challenge);
+        assert_eq!(s.challenge_best_score, 2400);
+        assert_eq!(s.challenge_fastest_win_seconds, 480);
+        assert_eq!(s.classic_best_score, 0);
+        assert_eq!(s.zen_best_score, 0);
+    }
+
+    #[test]
+    fn time_attack_win_does_not_touch_per_mode_bests() {
+        let mut s = StatsSnapshot::default();
+        s.update_per_mode_bests(9999, 1, GameMode::TimeAttack);
+        assert_eq!(s.classic_best_score, 0);
+        assert_eq!(s.zen_best_score, 0);
+        assert_eq!(s.challenge_best_score, 0);
+        assert_eq!(s.classic_fastest_win_seconds, 0);
+        assert_eq!(s.zen_fastest_win_seconds, 0);
+        assert_eq!(s.challenge_fastest_win_seconds, 0);
+    }
+
+    #[test]
+    fn per_mode_best_score_takes_max_across_calls() {
+        let mut s = StatsSnapshot::default();
+        s.update_per_mode_bests(500, 200, GameMode::Classic);
+        s.update_per_mode_bests(200, 200, GameMode::Classic);
+        s.update_per_mode_bests(900, 200, GameMode::Classic);
+        assert_eq!(s.classic_best_score, 900);
+    }
+
+    #[test]
+    fn per_mode_fastest_uses_zero_aware_min() {
+        // First Classic win: 240s. Field starts at 0 (no win yet) — we
+        // must adopt 240, not stay at 0 like a naive `min` would.
+        let mut s = StatsSnapshot::default();
+        s.update_per_mode_bests(100, 240, GameMode::Classic);
+        assert_eq!(s.classic_fastest_win_seconds, 240);
+        // Faster Classic win replaces it.
+        s.update_per_mode_bests(100, 120, GameMode::Classic);
+        assert_eq!(s.classic_fastest_win_seconds, 120);
+        // Slower Classic win does not.
+        s.update_per_mode_bests(100, 300, GameMode::Classic);
+        assert_eq!(s.classic_fastest_win_seconds, 120);
+    }
+
+    #[test]
+    fn negative_score_treated_as_zero_in_per_mode() {
+        let mut s = StatsSnapshot::default();
+        s.update_per_mode_bests(-50, 240, GameMode::Classic);
+        assert_eq!(s.classic_best_score, 0);
+        // Time still recorded — a win with a low score is still a win.
+        assert_eq!(s.classic_fastest_win_seconds, 240);
+    }
+
+    #[test]
+    fn legacy_stats_without_per_mode_fields_deserializes_to_zero() {
+        // A pre-per-mode `stats.json` must still deserialise cleanly:
+        // every new field falls back to 0 via `#[serde(default)]` so
+        // updating the binary never wipes the player's old stats file.
+        let legacy_json = r#"{
+            "games_played": 12,
+            "games_won": 5,
+            "games_lost": 7,
+            "win_streak_current": 1,
+            "win_streak_best": 3,
+            "avg_time_seconds": 240,
+            "fastest_win_seconds": 180,
+            "lifetime_score": 8500,
+            "best_single_score": 2200,
+            "draw_one_wins": 4,
+            "draw_three_wins": 1,
+            "last_modified": "2026-04-29T12:00:00Z"
+        }"#;
+
+        let s: StatsSnapshot = serde_json::from_str(legacy_json)
+            .expect("legacy payload must deserialise without per-mode fields");
+
+        // Pre-existing fields kept their values.
+        assert_eq!(s.games_played, 12);
+        assert_eq!(s.best_single_score, 2200);
+        assert_eq!(s.fastest_win_seconds, 180);
+
+        // Every new per-mode field defaulted to 0 ("no win yet").
+        assert_eq!(s.classic_best_score, 0);
+        assert_eq!(s.classic_fastest_win_seconds, 0);
+        assert_eq!(s.zen_best_score, 0);
+        assert_eq!(s.zen_fastest_win_seconds, 0);
+        assert_eq!(s.challenge_best_score, 0);
+        assert_eq!(s.challenge_fastest_win_seconds, 0);
+    }
 }