- Add WorktreePath and WorktreeBranch fields to TaskDTO
- Add WorktreeLookup interface to TaskController for enriching task responses
- Add GetWorktreeInfo method to worktree.Manager implementing WorktreeLookup
- Wire worktree manager to task controller in main.go
- Add worktree_path and worktree_branch to frontend Task type
- Display worktree path with copy button in TaskTopBar when worktree exists
- Show worktree branch in tooltip for easy reference