wt init dependency prompt redraws on arrow keys in narrow terminals

[notdp]

Environment

• OS: macOS (Darwin 24.6.0)
• worktree.sh version: 0.1.0
• Terminal width: about 80 columns or narrower

Steps to Reproduce

1. Open a terminal pane and shrink it to roughly 80 columns.
2. Run wt init inside a Git repository and answer the initial prompts.
3. When the wizard reaches "Which command installs dependencies?", press the Up or Down arrow to change the selection.

Actual Result

• Every arrow key press repaints the whole prompt; the "Use arrow keys..." helper line flashes repeatedly and the menu flickers, making the active option hard to track even though it eventually updates.

Expected Result

• The prompt should only update the highlighted option, without full-screen redraws, regardless of terminal width.

Additional Notes

• Widening the terminal beyond about 80 columns prevents the redraw storm.