feat: add productivity apps wizard step (Alfred, Raycast, Radial, ExtraBar)

## Feature Request

Add a dedicated wizard step for macOS productivity app selection and configuration.

## Apps to Support
- [ ] Alfred
- [ ] Raycast
- [ ] Radial
- [ ] ExtraBar

## Acceptance Criteria
- Wizard step allows user to select productivity launcher(s)
- tilde installs via Homebrew cask
- App-specific dotfiles/config linked where applicable
- Step is optional (marked opt)