Queue worker used pcntl_async_signals which delivers signals mid-fiber,
causing "Cannot switch fibers in current execution context" on PHP 8.5
when using amphp/redis (fiber-based Redis driver) with Horizon.

Signal handling now uses Revolt EventLoop::onSignal() and
EventLoop::delay() for timeouts, with fiber-aware sleep via
EventLoop::getSuspension(). Falls back to pcntl when Revolt is absent.