Identify and implement top five code reduction

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 :)

Measured the whole tree for code-reduction: non-test source holds 25 exactly duplicated lines of 725K; the five large candidates (Windows surface 13.9K, four tools' selftests 2.3K, community doctrine 740, identity _legacy_ columns, unused-feature retirement) are product decisions, the last needing the CP reader the broker refused. Folded the two real same-home twins (forge_ci _str, customers PriceOut) in PR #7486, lane-merged as e4843268ab. Quick gate and 43 changed-area tests green; no UI surface affected. Memory: used mem-31667, 31415, 31297, 27843, 12787; 0 proposals landed.