refactor: replace sequential wizard with iterative QuickPick for start with options

Replace 12 sequential input prompts with a single iterative QuickPick menu.
Users see all options with defaults, edit only what they need, and launch
when ready.

Add config file picker with smart defaults:
- Active editor config file takes priority
- Falls back to workspace devproxyrc.json
- Otherwise uses install folder default
- Picker shows all workspace config files for override

Author: garrytrinder