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/deck.rs

@@ -0,0 +1,159 @@
+use rand::{seq::SliceRandom, SeedableRng};
+use rand::rngs::StdRng;
+use crate::card::{Card, Rank, Suit};
+use crate::pile::{Pile, PileType};
+
+const ALL_SUITS: [Suit; 4] = [Suit::Clubs, Suit::Diamonds, Suit::Hearts, Suit::Spades];
+const ALL_RANKS: [Rank; 13] = [
+    Rank::Ace, Rank::Two, Rank::Three, Rank::Four, Rank::Five,
+    Rank::Six, Rank::Seven, Rank::Eight, Rank::Nine, Rank::Ten,
+    Rank::Jack, Rank::Queen, Rank::King,
+];
+
+/// A standard 52-card deck.
+pub struct Deck {
+    pub cards: Vec<Card>,
+}
+
+impl Deck {
+    /// Creates an unshuffled deck with all 52 unique cards (id 0–51).
+    pub fn new() -> Self {
+        let mut cards = Vec::with_capacity(52);
+        let mut id = 0u32;
+        for &suit in &ALL_SUITS {
+            for &rank in &ALL_RANKS {
+                cards.push(Card { id, suit, rank, face_up: false });
+                id += 1;
+            }
+        }
+        Self { cards }
+    }
+
+    /// Shuffles the deck in-place using Fisher-Yates with a seeded `SmallRng`.
+    /// The same seed always produces the same order on any platform.
+    pub fn shuffle(&mut self, seed: u64) {
+        let mut rng = StdRng::seed_from_u64(seed);
+        self.cards.shuffle(&mut rng);
+    }
+}
+
+impl Default for Deck {
+    fn default() -> Self {
+        Self::new()
+    }
+}
+
+/// Deals a standard Klondike layout from a pre-shuffled deck.
+///
+/// Returns 7 tableau piles and the remaining stock pile.
+/// Column `i` contains `i + 1` cards; only the top card is face-up.
+/// Stock receives the remaining 24 cards, all face-down.
+pub fn deal_klondike(deck: Deck) -> ([Pile; 7], Pile) {
+    let mut tableau: [Pile; 7] = core::array::from_fn(|i| Pile::new(PileType::Tableau(i)));
+    let mut cards = deck.cards.into_iter();
+
+    for (col, pile) in tableau.iter_mut().enumerate() {
+        for row in 0..=col {
+            let mut card = cards.next().expect("deck has 52 cards");
+            card.face_up = row == col;
+            pile.cards.push(card);
+        }
+    }
+
+    let mut stock = Pile::new(PileType::Stock);
+    stock.cards.extend(cards);
+    (tableau, stock)
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn deck_new_has_52_cards() {
+        assert_eq!(Deck::new().cards.len(), 52);
+    }
+
+    #[test]
+    fn deck_new_has_unique_ids() {
+        let deck = Deck::new();
+        let mut ids: Vec<u32> = deck.cards.iter().map(|c| c.id).collect();
+        ids.sort_unstable();
+        ids.dedup();
+        assert_eq!(ids.len(), 52);
+    }
+
+    #[test]
+    fn deck_new_has_all_suits_and_ranks() {
+        let deck = Deck::new();
+        for suit in ALL_SUITS {
+            for rank in ALL_RANKS {
+                assert!(
+                    deck.cards.iter().any(|c| c.suit == suit && c.rank == rank),
+                    "missing {rank:?} {suit:?}"
+                );
+            }
+        }
+    }
+
+    #[test]
+    fn same_seed_produces_same_order() {
+        let mut d1 = Deck::new(); d1.shuffle(42);
+        let mut d2 = Deck::new(); d2.shuffle(42);
+        assert_eq!(d1.cards, d2.cards);
+    }
+
+    #[test]
+    fn different_seeds_produce_different_orders() {
+        let mut d1 = Deck::new(); d1.shuffle(1);
+        let mut d2 = Deck::new(); d2.shuffle(2);
+        assert_ne!(d1.cards, d2.cards);
+    }
+
+    #[test]
+    fn deal_klondike_correct_tableau_sizes() {
+        let mut deck = Deck::new(); deck.shuffle(0);
+        let (tableau, stock) = deal_klondike(deck);
+        for (i, pile) in tableau.iter().enumerate() {
+            assert_eq!(pile.cards.len(), i + 1, "col {i} wrong size");
+        }
+        assert_eq!(stock.cards.len(), 24);
+    }
+
+    #[test]
+    fn deal_klondike_top_cards_are_face_up() {
+        let mut deck = Deck::new(); deck.shuffle(0);
+        let (tableau, _) = deal_klondike(deck);
+        for pile in &tableau {
+            assert!(pile.cards.last().unwrap().face_up);
+        }
+    }
+
+    #[test]
+    fn deal_klondike_non_top_cards_are_face_down() {
+        let mut deck = Deck::new(); deck.shuffle(0);
+        let (tableau, _) = deal_klondike(deck);
+        for pile in &tableau {
+            for card in &pile.cards[..pile.cards.len().saturating_sub(1)] {
+                assert!(!card.face_up);
+            }
+        }
+    }
+
+    #[test]
+    fn deal_klondike_stock_is_face_down() {
+        let mut deck = Deck::new(); deck.shuffle(0);
+        let (_, stock) = deal_klondike(deck);
+        assert!(stock.cards.iter().all(|c| !c.face_up));
+    }
+
+    #[test]
+    fn deal_klondike_all_52_cards_present() {
+        let mut deck = Deck::new(); deck.shuffle(99);
+        let (tableau, stock) = deal_klondike(deck);
+        let mut ids: Vec<u32> = stock.cards.iter().map(|c| c.id).collect();
+        for pile in &tableau { ids.extend(pile.cards.iter().map(|c| c.id)); }
+        ids.sort_unstable();
+        assert_eq!(ids, (0u32..52).collect::<Vec<_>>());
+    }
+}