Brummel
2b56e090a9
Ships C12 orchestration axis 2 (optimize): pick the single best point of a sweep family by a named RunMetrics field. The GREEN half of the RED-first iteration whose executable-spec landed in the previous commit. optimize(&SweepFamily, metric) -> Result<SweepPoint, RegistryError> returns the whole winning SweepPoint — its params coordinate AND its RunReport — because the caller needs the params that won, not just the metric. "Best" is fixed per metric (total_pips higher-is-better; max_drawdown / exposure_sign_flips lower-is-better); ties resolve to the earliest enumeration-order point (the family is in odometer order, and only a strictly-better later point displaces the incumbent). Single source of truth for "best", as #67 required ("reuse rank_by; do not fork"): rank_by's per-metric direction is extracted into a private `metric_cmp` helper that resolves the boundary metric *name* to a closed `enum Metric` once and returns one comparator closure. Both rank_by (sort by it) and optimize (argmax via `reduce`, strictly-better-displaces) now call it, so the per-metric direction lives in exactly one match. rank_by is behaviour-preserving — its existing tests pass unchanged. The sweep executor is untouched. No caller-supplied `direction`: one definition of best per metric, consistent with the shipped rank_by invariant (a caller direction would admit incoherent asks like the worst max_drawdown). An unknown metric is UnknownMetric. A SweepFamily is non-empty by construction (EmptyAxis is rejected upstream), so the argmax always yields a winner. CLI surface: the "pick the best" view is already served by `aura runs rank <metric>`, whose first line is the optimum over the persisted registry; optimize() is the new *programmatic* axis-2 entry, for World programs that hold a live SweepFamily and need the winning params back in-process — which the registry/RunReport path cannot give. No redundant CLI command added. closes #67