GenerativeUiInterfaceGetComponentsMessage

Call this first. It lists every component this device can render, with the JSON Schema of its properties and how it renders, plus the A2UI catalog ids, the payload size limit and the screen (`display`: 960 by 540 dp at ten-foot viewing distance on a 1080p TV, so design with large text and few items). The answer comes from the device's registration with Port OS, so it works while the device is asleep. Usage order for the interface: get-components, show-surface with the whole first UI, small update-surface calls, then close-surface. A device shows one surface at a time. Build only with the components returned here; interactive components (buttons, inputs), Video and AudioPlayer are not supported.