refactor: remove leftover redundancies after card_game migration

Post-migration audit found the card_game/klondike migration essentially
complete; these are the four small redundancies that remained:

- core: delete dead GameState::compute_time_bonus (zero callers; engine
  uses the klondike_adapter free fn directly)
- data: drop dead public re-exports load_latest_replay_from /
  save_latest_replay_to (no callers outside replay.rs); keep
  latest_replay_path (engine legacy migration still uses it)
- data+engine: lift win-XP scoring into a shared XpBreakdown so the
  win-summary modal breakdown and xp_for_win share one source of truth
  instead of duplicating the speed/no-undo constants
- engine: replace feedback_anim_plugin's private foundation_from_slot
  copy with the canonical klondike_adapter::foundation_from_slot

cargo test --workspace + clippy -D warnings green.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

solitaire_data/src/progress.rs

@@ -25,12 +25,34 @@ pub fn daily_seed_for(date: NaiveDate) -> u64 {
     y * 10_000 + m * 100 + d
 }
 
-/// XP awarded for winning a game.
+/// Component breakdown of the XP awarded for a win.
+///
+/// This is the single source of truth for win-XP scoring: [`xp_for_win`] sums
+/// it for the total, and UI that displays the individual lines (the win-summary
+/// modal) reads the parts from here so the breakdown can never drift from the
+/// total.
+#[derive(Debug, Clone, Copy, PartialEq, Eq)]
+pub struct XpBreakdown {
+    /// Flat base XP granted for any win.
+    pub base: u64,
+    /// Scaled fast-win bonus (10..=50 for sub-2-minute wins, else 0).
+    pub speed_bonus: u64,
+    /// Bonus for winning without using undo (25, else 0).
+    pub no_undo_bonus: u64,
+}
+
+impl XpBreakdown {
+    /// Total XP awarded: `base + speed_bonus + no_undo_bonus`.
+    pub fn total(self) -> u64 {
+        self.base + self.speed_bonus + self.no_undo_bonus
+    }
+}
+
+/// Component breakdown of the XP awarded for a win.
 ///
 /// Base 50 + scaled fast-win bonus (10..=50 for sub-2-minute wins) + 25 if
 /// the player did not use undo.
-pub fn xp_for_win(time_seconds: u64, used_undo: bool) -> u64 {
-    let base: u64 = 50;
+pub fn xp_breakdown(time_seconds: u64, used_undo: bool) -> XpBreakdown {
     let speed_bonus: u64 = if time_seconds >= 120 {
         0
     } else {
@@ -39,8 +61,16 @@ pub fn xp_for_win(time_seconds: u64, used_undo: bool) -> u64 {
         let scaled = 50_u64.saturating_sub(time_seconds.saturating_mul(40) / 120);
         scaled.max(10)
     };
-    let no_undo_bonus: u64 = if used_undo { 0 } else { 25 };
-    base + speed_bonus + no_undo_bonus
+    XpBreakdown {
+        base: 50,
+        speed_bonus,
+        no_undo_bonus: if used_undo { 0 } else { 25 },
+    }
+}
+
+/// XP awarded for winning a game. See [`xp_breakdown`] for the components.
+pub fn xp_for_win(time_seconds: u64, used_undo: bool) -> u64 {
+    xp_breakdown(time_seconds, used_undo).total()
 }
 
 /// Platform-specific default path for `progress.json`.