Function lumen_signal_set_float64 

#[unsafe(no_mangle)]
pub unsafe extern "C" fn lumen_signal_set_float64(
    name: *const c_char,
    value: f64,
) -> LumenStatus

Set a scalar signal to an IEEE-754 double, typed.

Pushes PropertyValue::F64 through the typed-property bus so the PropertyStore cell receives the typed variant directly.