feat(core): add pile, error, deck, rules, scoring modules with tests

Implements PileType/Pile, MoveError (thiserror), Deck with seeded shuffle,
deal_klondike layout, foundation/tableau placement rules, and Windows XP
Standard scoring — 41 tests, clippy clean.

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

solitaire_core/src/scoring.rs

@@ -0,0 +1,73 @@
+use crate::pile::PileType;
+
+/// Score delta for moving cards from `from` to `to`.
+///
+/// Windows XP Standard scoring:
+/// - +10 for any card reaching a foundation pile
+/// - +5 for a waste → tableau move
+/// - 0 for all other moves
+pub fn score_move(from: &PileType, to: &PileType) -> i32 {
+    match to {
+        PileType::Foundation(_) => 10,
+        PileType::Tableau(_) => {
+            if matches!(from, PileType::Waste) { 5 } else { 0 }
+        }
+        _ => 0,
+    }
+}
+
+/// Score penalty applied when the player uses undo: -15.
+pub fn score_undo() -> i32 {
+    -15
+}
+
+/// Time bonus added to the score on a win: `700_000 / elapsed_seconds`.
+/// Returns 0 when `elapsed_seconds` is 0 to avoid division by zero.
+pub fn compute_time_bonus(elapsed_seconds: u64) -> i32 {
+    if elapsed_seconds == 0 {
+        return 0;
+    }
+    (700_000u64 / elapsed_seconds).min(i32::MAX as u64) as i32
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use crate::card::Suit;
+
+    #[test]
+    fn move_to_foundation_scores_ten() {
+        assert_eq!(score_move(&PileType::Waste, &PileType::Foundation(Suit::Hearts)), 10);
+        assert_eq!(score_move(&PileType::Tableau(0), &PileType::Foundation(Suit::Clubs)), 10);
+    }
+
+    #[test]
+    fn waste_to_tableau_scores_five() {
+        assert_eq!(score_move(&PileType::Waste, &PileType::Tableau(3)), 5);
+    }
+
+    #[test]
+    fn tableau_to_tableau_scores_zero() {
+        assert_eq!(score_move(&PileType::Tableau(0), &PileType::Tableau(1)), 0);
+    }
+
+    #[test]
+    fn undo_penalty_is_negative_fifteen() {
+        assert_eq!(score_undo(), -15);
+    }
+
+    #[test]
+    fn time_bonus_at_100_seconds() {
+        assert_eq!(compute_time_bonus(100), 7000);
+    }
+
+    #[test]
+    fn time_bonus_at_zero_is_zero() {
+        assert_eq!(compute_time_bonus(0), 0);
+    }
+
+    #[test]
+    fn time_bonus_at_one_second() {
+        assert_eq!(compute_time_bonus(1), 700_000);
+    }
+}