I've been working on this split in a side project (https://github.com/rillmd/rill — vault layer on top of Claude Code). Git still handles the durable side for free, since the CLI agent just writes files and commits normally. The live side comes from Claude Code hooks (UserPromptSubmit / Stop / PostToolUse) appending to a plain activity-log.md that the Electron GUI tails. Cruder than Google Docs cursor presence, but cheap — and the log itself is just another markdown file in the vault, same data model as everything else.
One trade-off: going the other direction and letting the frontend detect edits via FSEvents-style watching runs straight into the reconciliation issues the Zettlr subthread is about. Hooks on the agent side are less elegant but sidestep the whole class.
It's still early stage, but I love their pitch so I'm following them with fingers crossed.