fix: reduce idle CPU wakeups and deferred-work polling

kernel/src/Hal/SmpBoot.cpp

@@ -218,6 +218,10 @@ namespace Smp {
         for (;;) {
             // Pick up thermal-governor frequency changes decided by the BSP.
             Hal::CpuPower::ApplyPolicyIfChanged();
+            // Runnable work sends this AP a reschedule IPI. Keep its periodic
+            // scheduler tick masked for the entire idle-context pass so long
+            // firmware waits do not keep generating useless timer interrupts.
+            Timekeeping::ApicTimerEnterApIdle();
             // Any idle core may run bounded USB/NIC bottom halves. Preserve
             // the AP's ACPI/MWAIT idle selection after servicing them.
             Timekeeping::ServiceDeferredWork();