feat: various power and thermal optimizations, fix Printers app regression

kernel/src/Timekeeping/ApicTimer.hpp

@@ -28,6 +28,10 @@ namespace Timekeeping {
     // Enable scheduler tick (called after scheduler is initialized)
     void EnableSchedulerTick();
 
+    // Enter one idle wait cycle for the current CPU. The BSP uses a
+    // one-shot LAPIC timer while idle; APs keep their existing simple wait.
+    void IdleOnce(bool hasMwait, volatile uint64_t* monitorAddr = nullptr);
+
     // Busy-wait sleep for the given number of milliseconds
     void Sleep(uint64_t ms);
 };