Add a configurable delay between when input is stopped and editor predictions are shown

[leftbones]

When I'm typing in VSCode, there appears to be a small delay between when I stop typing and when predictions are shown. That way I can go to a new line, press tab, keep going, whatever. If I want predictions, I stop and wait a tick, then they show up and I can press tab to accept them.

When I'm typing in Zed, predictions are shown immediately. So if I go to a new line and I want to indent, Copilot jumps in front of me and inserts some code I didn't want, thinking it did a good job.

I just want a delay, 300ms is all I'm asking. Please!