refactor(core): align Spider with upstream card_game idioms

Addresses upstream author review of the Spider core (PR #157):

- RNG: drop the hand-rolled SplitMix64 + Fisher-Yates; deals now use
  rand::rngs::StdRng seeded via seed_from_u64 + SliceRandom::shuffle,
  exactly like klondike::with_seed. solitaire_core gains the same
  pinned rand dep klondike uses (0.10.1, std_rng only — already in the
  lock, no new transitive deps). Deals for a given seed change; Spider
  has no persisted games yet, so nothing breaks.
- Enums over integers: pile indices and card counts in the instruction
  type are now SpiderTableau (Tableau1..Tableau10, with an ALL const)
  and RunLength (Run1..Run13); out-of-range piles and zero-card moves
  are unrepresentable. Rank comparisons use Rank::checked_add instead
  of u8 arithmetic.
- Fixed-size containers: build_deck returns Stack<104> instead of
  Vec<Card>; possible_instructions is a const-iterated SpiderIter +
  validity filter (klondike's KlondikeIter pattern) instead of
  collecting into a Vec.
- Upstream naming: SpiderGame -> Spider (matches Klondike),
  tableau_face_up/_down -> tableau_face_up_cards/_down_cards,
  stock_len -> stock() accessor, with_rng added alongside with_seed.
- Solver access: SpiderGameState now exposes session(), the same
  escape hatch GameState has — the wrapper no longer pretends to hide
  solve(), which SessionConfig budgets already gate.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

solitaire_core/src/lib.rs

@@ -25,8 +25,8 @@ pub use game_state::{DEFAULT_SOLVE_MOVES_BUDGET, DEFAULT_SOLVE_STATES_BUDGET, So
 // Spider rules (second `card_game::Game` implementation; engine UI is a
 // later phase — nothing outside solitaire_core consumes these yet).
 pub use spider::{
-    SpiderConfig, SpiderGame, SpiderGameState, SpiderInstruction, SpiderScoring, SpiderStats,
-    SpiderSuits,
+    RunLength, Spider, SpiderConfig, SpiderGameState, SpiderInstruction, SpiderIter, SpiderMove,
+    SpiderScoring, SpiderStats, SpiderSuits, SpiderTableau,
 };
 
 /// All four foundation slots, in slot order.