Summary

• Adds a new "Flushing stats to the server" section to the Achievements & Stats docs with storeStats() / store_stats() / StoreStats() examples for all three engines (JS, Godot, Unity)
• Explains the debounce behavior (5s window, leading + trailing) and page-unload safety net
• Updates the existing debounce note to reference storeStats() as the explicit flush option