#3477 [GUI] Desktop notification when agent needs approval in Manual mode

Description

**Feature Request: Desktop notification when agent needs approval in Manual mode**

In Manual mode, approval cards only appear inside the chat.  
If the window is in the background, it’s easy to miss that the agent is waiting.

An optional system notification (Windows toast / macOS Notification Center, etc.) when an approval is needed would make Manual mode much more practical.

Strata version: 0.2.1

(Translated with AI)