vTaskDelete(nullptr) does not unwind the C++ stack, so the RAII
HalPowerManager::Lock destructor never ran -- permanently holding the
lock and preventing low-power mode. Fix by wrapping the lock in a block
scope that exits before vTaskDelete().
Revert the setPowerSaving(false) calls in the clock refresh block; the
RenderLock already handles CPU frequency during display updates.
Made-with: Cursor
