Function decider 

pub fn decider() -> impl Fn(&str) -> Directive + Send + Sync + 'static

The supervisor decider used by DeviceActor to route ContextActor failures (§5.11).

Rakka 0.2.0 ships a typed SupervisorOf<C> trait (see the [device_supervisor] impl below) that lets DeviceActor pattern- match on &GpuError directly. The closure-based decider() here is retained as the runtime fallback used by device_supervisor_strategy — actors without an explicit SupervisorOf<C> impl fall through to this string-matching path, and panicking remains the failure transport regardless (since Actor::handle returns ()). The typed trait simply replaces the receive-side parsing.