fix: revert // to / in deck.gd (GDScript 4 does not support // operator)

The INTEGER_DIVISION warning in deck.gd:19 is a false positive - both
operands are int, so / performs integer division correctly in GDScript 4.
Using // caused a parse error (Expected expression after '/' operator),
which cascaded to GameController/TrainingController resolution failure.

tests/hello.gd.uid

@@ -0,0 +1 @@
+uid://lod5euxb1cwb

tests/quick_test.gd.uid

@@ -0,0 +1 @@
+uid://dr7imryh5wia8

tests/run_validation.gd.uid

@@ -0,0 +1 @@
+uid://crfk8i35o3o6d

tests/test_cards.gd.uid

@@ -0,0 +1 @@
+uid://bprfm0f45hu8e

tests/test_deck.gd.uid

@@ -0,0 +1 @@
+uid://cisvuuexcmhei

tests/test_deck_load.gd

@@ -0,0 +1,9 @@
+extends SceneTree
+
+func _initialize():
+	var d = load("res://src/core/deck.gd")
+	if d:
+		print("Deck loaded: ", d)
+	else:
+		print("FAIL: Deck not found")
+	quit()

tests/test_game_state.gd.uid

@@ -0,0 +1 @@
+uid://chwtpkp06q4no

tests/test_hand_evaluator.gd.uid

@@ -0,0 +1 @@
+uid://cefkmiwlb6dlc

tests/test_rule_engine.gd.uid

@@ -0,0 +1 @@
+uid://ryaamcy0nefy

tests/test_training_controller.gd

@@ -0,0 +1,14 @@
+extends SceneTree
+
+func _initialize():
+	var t = load("res://src/game/game_controller.gd")
+	if t:
+		print("GameController loaded: ", t)
+	else:
+		print("FAIL: GameController not found")
+	var tc = load("res://src/game/training_controller.gd")
+	if tc:
+		print("TrainingController loaded: ", tc)
+	else:
+		print("FAIL: TrainingController not found")
+	quit()

tests/validate_project.gd.uid

@@ -0,0 +1 @@
+uid://bgbmacvuo7rjd