Support @ in New Task Popup

[oxysoft]

Hello!

The New Task popup is quite useful for springboarding from trad coding where precision and rigor is required, to vibe coding for more delegatable tasks. It's less jarring than having to shift focus to the chat sidebar, especially when the developer may walk back that decision and return to the code instead.

BUT! it does not support @ since it uses a built-in basic VS Code popup. Maybe we need a custom popup, if the VS Code platform doesn't allow augmenting this popup with the same input field as in the kilo panel.