Add gas bomber skill-shot vessel

tests/test_multi_resource_supply.gd

@@ -0,0 +1,42 @@
+extends SceneTree
+
+
+func _initialize() -> void:
+	var state: Node = root.get_node("GameState")
+	state.buildings.clear()
+	state.extractors.clear()
+	state.transporters.clear()
+	state.stored_vessels.clear()
+	state.reset_progression()
+	state.rocks = 0
+	state.gas = 30
+	state.build_time_scale = 0.01
+
+	state.add_building(GameState.BUILDING_MOTHERSHIP, Vector2.ZERO)
+	state.add_building(GameState.BUILDING_TRANSPORT_HUB, Vector2.ZERO)
+	var lab_id: int = state.add_building(GameState.BUILDING_SHIP_LAB, Vector2(120, 0))
+	if not state.queue_lab_research(lab_id, "unlock_gas_bomber"):
+		_fail("could not queue gas research")
+		return
+	if state.outstanding_resource_cost(lab_id, GameState.RESOURCE_GAS) != 30:
+		_fail("lab did not request 30 gas")
+		return
+
+	# Large steps make each physical leg complete in one call; multiple calls
+	# still exercise dispatch -> bank pickup -> lab delivery -> hub return.
+	for i in range(12):
+		state._advance_transporters(10.0)
+		state._advance_lab_research(10.0)
+	if not state.vessel_is_unlocked(GameState.VESSEL_GAS_BOMBER):
+		_fail("hub transporters did not deliver gas to research")
+		return
+	if state.gas != 0 or state.building_resource(lab_id, GameState.RESOURCE_GAS) != 0:
+		_fail("gas was not consumed at the lab")
+		return
+	print("TEST_MULTI_RESOURCE_SUPPLY: PASS")
+	quit(0)
+
+
+func _fail(message: String) -> void:
+	print("TEST_MULTI_RESOURCE_SUPPLY: FAIL (%s)" % message)
+	quit(1)