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 :)

Net −318 LOC via 4 reductions: one shared /worktrees e2e gate oracle, tombstones out of 11 e2e specs, a vitest-owned assertion and dead re-exports out of e2e, two unused jaahd fixtures. 5th (shared Audit session row, ~300 LOC) deferred. Measured ceiling: no massive cut exists without deleting live features. Quick gate green, 14 e2e passed live, lanes pass; PR #7916 queued.