//! The device's top safe-area inset (notch / Dynamic Island), in points.
//!
//! Returns the raw inset, or `0.0` when unavailable (off-iOS, or before the key
//! window exists). The caller owns the fallback policy — a layout typically
//! clamps to a notch-class constant when this reports `0.0` and adds its own
//! breathing-room margin.