test: add GUT test files for core modules (Card, Deck, HandEvaluator, RuleEngine, GameState)

tests/test_deck.gd

@@ -0,0 +1,35 @@
+extends GutTest
+
+func test_deck_has_108_cards():
+    var deck := Deck.create()
+    assert_eq(deck.remaining(), 108)
+
+func test_deal_reduces_count():
+    var deck := Deck.create()
+    var cards := deck.deal(27)
+    assert_eq(cards.size(), 27)
+    assert_eq(deck.remaining(), 81)
+
+func test_shuffle_deterministic():
+    var seed := 12345
+    var deck1 := Deck.create(seed)
+    var deck2 := Deck.create(seed)
+    var hand1 := deck1.deal(108)
+    var hand2 := deck2.deal(108)
+    for i in range(108):
+        assert_eq(hand1[i].card_id, hand2[i].card_id)
+
+func test_deal_empty_deck():
+    var deck := Deck.create()
+    deck.deal(108)
+    var extra := deck.deal(1)
+    assert_eq(extra.size(), 0)
+
+func test_deck_card_ids_unique():
+    var deck := Deck.create()
+    var all_cards := deck.deal(108)
+    var ids := {}
+    for c in all_cards:
+        assert_false(ids.has(c.card_id))
+        ids[c.card_id] = true
+    assert_eq(ids.size(), 108)