feat: add structured economic events

tests/food_storage_loop_test.gd

@@ -110,6 +110,21 @@ func _run() -> void:
 		is_equal_approx(conserved_food, 9.0),
 		"Exactly one food unit should leave the world when eaten"
 	)
+	_check_economic_event_chain(manager)
+
+	var restored: Node = load("res://simulation/SimulationManager.gd").new()
+	restored.debug_logs = false
+	root.add_child(restored)
+	restored.set_process(false)
+	_check(
+		restored.restore_state_from_json(manager.serialize_state()),
+		"Economic events should restore with the simulation"
+	)
+	_check(
+		restored.economic_events.size() == manager.economic_events.size()
+		and restored.next_event_id == manager.next_event_id,
+		"Economic event history and its next ID should round-trip"
+	)
 
 	if failures.is_empty():
 		print("[TEST] Food storage loop passed")
@@ -122,3 +137,45 @@ func _run() -> void:
 func _check(condition: bool, message: String) -> void:
 	if not condition:
 		failures.append(message)
+
+func _check_economic_event_chain(manager: Node) -> void:
+	var expected_types: Array[StringName] = [
+		SimulationIds.EVENT_RESOURCE_EXTRACTED,
+		SimulationIds.EVENT_STORAGE_DEPOSITED,
+		SimulationIds.EVENT_STORAGE_WITHDRAWN,
+		SimulationIds.EVENT_ITEM_CONSUMED
+	]
+	_check(
+		manager.economic_events.size() == expected_types.size(),
+		"Food transfer loop should emit one structured event per transfer"
+	)
+	if manager.economic_events.size() != expected_types.size():
+		return
+	for index in expected_types.size():
+		var event: EconomicEventRecord = manager.economic_events[index]
+		_check(
+			int(event.data["event_id"]) == index
+			and StringName(event.data["event_type"]) == expected_types[index]
+			and StringName(event.data["item_id"])
+				== SimulationIds.RESOURCE_FOOD,
+			"Economic event order, identity, and item should be deterministic"
+		)
+	_check(
+		is_equal_approx(
+			float(manager.economic_events[0].data["amount"]),
+			2.0
+		)
+		and is_equal_approx(
+			float(manager.economic_events[1].data["amount"]),
+			2.0
+		)
+		and is_equal_approx(
+			float(manager.economic_events[2].data["amount"]),
+			1.0
+		)
+		and is_equal_approx(
+			float(manager.economic_events[3].data["amount"]),
+			1.0
+		),
+		"Economic events should record exact transferred quantities"
+	)