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/Cargo.toml

@@ -16,6 +16,11 @@ serde     = { workspace = true }
 thiserror = { workspace = true }
 klondike  = { workspace = true }
 card_game = { workspace = true }
+# Deliberately NOT the workspace rand (0.9): this pins the exact dep the
+# upstream `klondike` crate uses, so `SeedableRng`/`SliceRandom` resolve
+# against the same crate version as `klondike::Rng` and Spider deals go
+# through the identical shuffle stack as Klondike deals.
+rand      = { version = "0.10.1", default-features = false, features = ["std_rng"] }
 
 [lints]
 workspace = true