Update recommendations for synchronization methods

added std::atomic

Author: softhack007

AGENTS.md

@@ -163,7 +163,7 @@ Background Info:
 - Use FreeRTOS mutexes, semaphores or queues when true concurrent access from multiple FreeRTOS tasks is possible, and race-conditions can lead to unexpected behaviour.
 - **Avoid `portENTER_CRITICAL()` / `portEXIT_CRITICAL()`**, as these functions stall the complete system and may cause LEDs flickering. Prefer FreeRTOS mutexes, semaphores or queues.
 - **Important**: Not every shared resource needs a mutex. Some synchronization is guaranteed by the overall control flow, for example when function calls are sequenced within the same loop iteration.
-- Consider RAII as an alternative to  mutexes or semaphores.
+- Consider using `std::atomic` or RAII scoped guards as alternatives to mutexes, semaphores or queues.
 
 ## Web UI Code Style (wled00/data/)