The default clone base directory was 'takt-worktree' (singular), which is
inconsistent since multiple worktrees are created inside it.
Changed to 'takt-worktrees' (plural) while maintaining backward compatibility:
- If existing 'takt-worktree' directory exists, continue using it
- New installations will use 'takt-worktrees'
- Explicit worktree_dir config always takes priority
2e72054c0d