Existing clones for a new canvas

When you add a repository in the Configuration dialog, its row now shows whether its agents work in worktrees or clones, as a switch. Choosing clones shows the clone fields right there, including the field for existing clones, one per line. Before, those fields only appeared for a repository that already worked in clones, and the choice was folded away in its settings, so a new canvas could not be pointed at clones you already have without asking for help.