Setup Flow Refresh Phase 4 (SFR4)

In phase four of the Setup Flow Refresh epic we'll tackle complex architectural aspects for long-term improvements (e.g., sharing markup, styling, and code between the plugin and service), and address various nice-to-haves that were not implemented for the initial release.

Start by reviewing the Setup Flow Refresh epic and its existing plugin and service implementations. Identify the specific architectural or nice-to-have item to pursue, then define its affected markup, styling, or code and the checks that establish completion.

Written by the indexing model from the issue text.