Implement Top Five Repo Code Reductions

Identify top 5 opportunities to massively reduce the amount of code (lines of code) in any part of the repo: - Similar functionality that can be unified and reused - Code that has been valuable but no more - A front end component or a group of them duplicate another component/page functionality. Use the most modern and nice looking - etc. Now implement them :)

Top 5 dedupes implemented: net −350 lines over 88 files (api/tools test helpers, actor columns, atomic JSON writer, adapter/guard/web scaffolding). Full gate green; PR #5381 merged, Jaah Deploy succeeded. Larger cuts are fleet/product-gated (named in report); UI notes recorded there since task_create is 403 for coder.