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 :)

Full-repo reduction census (7 tools + 5 recon sweeps over 1.6M lines): no dead code, 0.02% clones; the five massive levers (prose ~200k, test volume 12-18k, cloud SDKs ~21k, OpenAPI web types 6-9k, compat arms 1-2k) are owner decisions, priced in the report. Folded the last safe twins (initials rule, URL filters hook, atomic replace, join-row mixin; -33 source lines) + 2 pinning tests. Quick gate green, 3 blind lanes pass, visual check done. PR #7949 queued in the merge lane. Memory: used mem-25288, mem-36366; proposed 1 qa.