Add j/k navigation for multiple-choice prompt UI in the CLI

### Describe the feature or problem you'd like to solve

Lots of applications use keyboard-friendly vi-like navigation. It would be great to be able to use j/k to navigation multiple choice options

### Proposed solution

When seeing a menu like this, let `j` and `k` do the same thing as up and down.

### Example prompts or workflows

_No response_

### Additional context

_No response_

No file or test is named. Start by locating the CLI's multiple-choice prompt implementation and its existing up/down keyboard handling; done means j and k move through options exactly as the corresponding arrow keys do, with relevant tests passing.

Written by the indexing model from the issue text.