fix: enforce village resource invariants

tests/food_storage_loop_test.gd

@@ -112,6 +112,7 @@ func _run() -> void:
 		"Exactly one food unit should leave the world when eaten"
 	)
 	_check_economic_event_chain(manager)
+	_test_wood_work_requires_material()
 
 	var restored: Node = load("res://simulation/SimulationManager.gd").new()
 	restored.debug_logs = false
@@ -179,3 +180,48 @@ func _check_economic_event_chain(manager: Node) -> void:
 		),
 		"Economic events should record exact transferred quantities"
 	)
+
+
+func _test_wood_work_requires_material() -> void:
+	var manager: Node = load("res://simulation/SimulationManager.gd").new()
+	manager.debug_logs = false
+	root.add_child(manager)
+	manager.set_process(false)
+	var woodpile: StorageStateRecord = manager.get_woodpile()
+	woodpile.withdraw(SimulationIds.RESOURCE_WOOD, 1000.0)
+	woodpile.deposit(SimulationIds.RESOURCE_WOOD, 0.5)
+	manager._sync_village_wood()
+	var npc: SimNPC = manager.npcs[0]
+	var safety_before: float = manager.village.safety
+
+	npc.set_task(SimulationIds.ACTION_PATROL, 1.0)
+	npc.start_working()
+	manager.simulate_tick()
+	_check(
+		(
+			is_equal_approx(manager.village.safety, safety_before)
+			and is_equal_approx(woodpile.get_amount(SimulationIds.RESOURCE_WOOD), 0.5)
+		),
+		"Patrol should not consume partial wood or create safety when its full cost cannot be paid"
+	)
+
+	manager.add_wood(1.5)
+	_check(
+		(
+			is_equal_approx(woodpile.get_amount(SimulationIds.RESOURCE_WOOD), 2.0)
+			and is_equal_approx(manager.village.wood, 2.0)
+		),
+		"Wood changes should update authoritative storage and the village projection"
+	)
+	var knowledge_before: float = manager.village.knowledge
+	npc.set_task(SimulationIds.ACTION_STUDY, 1.0)
+	npc.start_working()
+	manager.simulate_tick()
+	_check(
+		(
+			is_equal_approx(woodpile.get_amount(SimulationIds.RESOURCE_WOOD), 1.0)
+			and manager.village.knowledge > knowledge_before
+		),
+		"Funded study should consume one wood and produce knowledge"
+	)
+	manager.free()