Offer maintained-population top-k candidates in Pass 1 #681

Pass 1 does not offer the maintained-population (current-series) top-k candidate (MaintainPopulation / EvaluatePopulation, #573). Only the legacy search proposed it, through MaintainedPopulationStrategy. It is not reachable on main today.

To do: generate it as a per-computation candidate for current-series top-k (and the other population intents), and implement it in physical ASAP-aware optimization. Materialization comes from #604 (G8).

Found in the #676 capability audit.