Reduce codebase size through refactoring and consolidation

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 :)

Round six of dedup: tree is clone-free, so retired four closed compatibility windows on a live fleet census (every node >= v1.2.4842): NodeLink v1 wires, JAAH_AGY_HOOKS alias, projects.fleet_enabled, EmailMailbox (hidden, dropped next release). 37 files, +194/-423. Quick gate, 2300+ API tests, review lanes pass. PR #7391 queued to the merge lane. Deferred: identity dual-write contraction, automation child bridging, worktree-agents reaper. Memory: used mem-22663; proposed 1 gotcha.