fix: reduce idle CPU wakeups and deferred-work polling

kernel/src/Sched/Scheduler.cpp

@@ -1284,6 +1284,15 @@ namespace Sched {
         uint8_t* oldFpu = (oldSlot >= 0) ? processTable[oldSlot].fpuState : nullptr;
         uint8_t* newFpu = processTable[next].fpuState;
 
+        if (oldSlot < 0) {
+            // AP idle loops mask their local periodic timer. Rearm it before
+            // dispatching user work so preemption resumes with the process.
+            // Also pick up a thermal-governor policy epoch that may have
+            // changed while this CPU remained asleep without timer ticks.
+            Hal::CpuPower::ApplyPolicyIfChanged();
+            Timekeeping::ApicTimerLeaveApIdle();
+        }
+
         LoadUserFsBase(cpu, processTable[next].fsBase);
 
         // DO NOT release schedLock here! It is held across the context