Support worktree-based workflows for session matching

[danielstarman]

I'm evaluating hunk for reviewing agent-authored code in a worktree-first workflow. Agents work in isolated worktrees while I review from a separate terminal. This is a natural fit for hunk's split-window model (agent annotates, I read), but session matching breaks across worktrees.

The issue: hunk session commands match by git rev-parse --show-toplevel, which returns a different path for each worktree. An agent in /tmp/worktree-feature-x can't annotate a hunk instance running in /home/me/repo even though they're the same repository.

Happy to take a crack at a PR if you're open to it.

[benvinegar]

Thanks for pointing this out! Happy to review a PR.