I took a similar "own the terminal" approach with Pane (https://runpane.com), but organized around git worktrees instead of splits. Each feature gets its own isolated worktree with N terminals, so agents never step on each other's files. The worktree lifecycle is fully automated.
Curious how you handle the case where someone is running 5+ agents on different features simultaneously? That's where the worktree isolation really shines vs. splits in a single repo checkout.
Repo: https://github.com/Dcouple-Inc/Pane (AGPL-3.0)