Alarm / countdown / ring logic moves from UITask to ui-core/ClockEngine.h
unchanged. New ui-core/UiEvents.h: fixed-size Core -> frontend event
queue; UITask::tickCore() runs UiCore::loop() and reacts to ClockAlert /
ClockRingEnded (wake, alert overlay, melody). ClockToolsScreen API unchanged.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>