Identify and implement five major 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 (vulture, import-graph orphans, router walk, export + exact-twin censuses, test audit): no semantics-preserving fold left above the 7 exact twins folded in PR #7510 (merged 65455cedc, net −29 lines; deploy 41215657818 succeeded). The five cuts that would move the number are owner decisions, named with their gate in the report: generated API types (2.2–2.9K, ADR), legacy shared root + NodeLink v1 wire (500–800, fleet read refused to this task), AdminUser dual-write contraction (non-additive migration), lint baselines (2.9K JSON). Quick gate green; review lane pass; visual check done, surfaces unchanged. Memory: used mem-31667, mem-31415; proposed 1 gotcha.