bug: inconsistent preference saving in wizards

### Problem
Preferences are inconsistently saved. In the TUI, sometimes going back will save my previous selection, sometimes it wont. Ex. name value is not stored on add agent flow, create/import is, then pyhon/typescript isn't.

### Definition of Done
- make it consistently save preferences across different wizards (ideally through shared implementation).

Start by tracing how the TUI saves preferences when moving back through the add agent, create, and import wizard flows. Compare the name value and Python/TypeScript paths to identify where saving differs. Done means preferences are saved consistently across the different wizards, ideally through a shared implementation.

Written by the indexing model from the issue text.