Function device_roofline 

pub fn device_roofline(
    device: &Device,
    measured: Option<&Roofline>,
    assumptions: &Roofline,
) -> DeviceRoofline

2026-09-30: The device’s constants: the measured ones when the registry points at them and they are measured (the class’s own manifest), else the datasheet with context_tokens taken from assumptions. A device without the FP4 MMA states its NVFP4 slot at the peak of fp4_fallback.