Include herdr in Kaku with some integrations

[trongthanh]

Recently I was introduced to herdr and find out it's a great tool for multi-agent working sessions.

I think it'll be a great-to-have to bundle herdr into next version of Kaku. And may be Kaku will provide some integrations for herdr such as toast notifications and an orchestrator on top to manage on-going agents...

I'll be using it more to find out what can we do with the integration. In the mean time, it's working well in Kaku (very much stable, and configurable like tmux).