feat(algorithms): add OnePlusOneEs (1+1)-ES with Rechenberg's one-fifth rule

Rechenberg 1973's elemental evolution strategy: one parent, one child
each generation, accept the child if it is no worse, and adapt the
mutation step size by tracking the success rate. If more than 1/5 of
recent moves were accepted the search is too cautious — multiply σ by
`step_increase` (typical 1.22). Below 1/5 — divide by the same factor.
At 1/5 — leave it alone. The success window has length `adaptation_period`.

Single-objective only. Vec<f64> only. Generic Gaussian step bounded by
the embedded `RealBounds`.

Why ship it: it's the smallest possible self-adapting evolution strategy
and a useful pedagogical / baseline endpoint. Pairs well as the budget
floor ("give me anything cheaper than CMA-ES").

src/prelude.rs

@@ -26,7 +26,7 @@ pub use crate::algorithms::{
     DifferentialEvolutionConfig, EpsilonMoea, EpsilonMoeaConfig,
     GeneticAlgorithm, GeneticAlgorithmConfig, Grea, GreaConfig, HillClimber, HillClimberConfig, Hype,
     HypeConfig, Ibea, IbeaConfig, Knea, KneaConfig, Moead, MoeadConfig, Mopso, MopsoConfig, Nsga2,
-    Nsga2Config, Nsga3, Nsga3Config, Paes, PaesConfig, ParticleSwarm, PesaII, PesaIIConfig,
+    Nsga2Config, Nsga3, Nsga3Config, OnePlusOneEs, OnePlusOneEsConfig, Paes, PaesConfig, ParticleSwarm, PesaII, PesaIIConfig,
     ParticleSwarmConfig, RandomSearch, RandomSearchConfig, Rvea, RveaConfig,
     SimulatedAnnealing,
     SimulatedAnnealingConfig, SmsEmoa, SmsEmoaConfig, Spea2, Spea2Config, TabuSearch,