Evaluate explicit, ordered optimization configurations through one shared
planner model. Add six editable presets, durable one-time legacy migration,
and consistent completed and cancelled plan provenance.
Include functional regressions and the agreed trace-removal and benchmark
follow-up specs. Performance acceptance remains in #78 under unchanged gates.
Refs: #70, #71, #72, #73, #74, #75, #76, #77, #78
