OptionalgetThe format the host prefers for a canvas swap chain — commonly
"bgra8unorm", not "rgba8unorm" (§60a; see webgpu-renderer.ts on
why that never widens RenderTargetFormat). Optional: a double may omit
it, and the backend falls back to "bgra8unorm".
Requests an adapter; resolves null where WebGPU is present but unusable.
Optionaloptions: { powerPreference?: string }
navigator.gpu, reduced to what this backend calls.