what does "retrofitting" git implies? I am confused by the agent-specific systems bit.

Why would agents need a specific versioning system?

Perhaps because Zed thinks it's a good idea?

https://zed.dev/blog/sequoia-backs-zed

DeltaDB (CRDT based)

I'm waiting for DeltaDB. Sounds game-changing to me. jj seems more like a facade for people who aren't good at git.