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
Brummel
2b56e090a9