message: Vulkan: repair headless swap chains.
  I broke this when migrating to FixedCapacityVector.
diff: @@ -402,6 +402,7 @@ VulkanSwapChain::VulkanSwapChain(VulkanContext& context, uint32_t width, uint32_
  swapchain = VK_NULL_HANDLE;
  // Somewhat arbitrarily, headless rendering is double-buffered.
  + color.reserve(2);
  color.resize(2);
  for (size_t i = 0; i < color.size(); ++i) {
  