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 :)

Five measured reductions on a scanner-clean tree (44 files, +634/-778): 26 identical-shape test groups parametrized; apt/dist/rpm/bootstrap serve tail, connect callback URLs, jaahd atomic writes, web JSON stubs and microvm test stubs single-homed. Quick gate + all changed suites green; PR #7388 merged by the lane, Jaah Deploy succeeded. Memory: none applied; proposed 0. MCP control tools hung; settled via jaah-call.