Identify and implement top 5 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 :)

11th sweep: tree at its code-reduction floor. jscpd, identifier-normalised clone scan, vulture, AST lookup-404 scan and types.ts dead-export scan find under 30 foldable lines; every recon lead already delegates to its shared home. No PR. Five remaining cuts are product-gated (legacy runtime, answer routes, telemetry/runs, older-jaahd fields: cp_psql census refused to this task, NodeGroupDialog in-page), named in the report with their unlocks. No UI surface affected. Memory: used mem-25288, mem-35380, mem-35895; proposed 1 qa (mem-36219).