Final iteration of cycle D: aura sweep persists each point's RunReport to
runs/runs.jsonl; aura runs list prints every stored record; aura runs rank
<metric> prints them best-first. sweep_report splits into a production
sweep_family() + a #[cfg(test)] renderer; process goldens run in a temp cwd so
persistence never dirties the repo; /runs/ is git-ignored.
refs #33
