feat(algorithms): add ParticleSwarm (canonical PSO) for Vec<f64>

Eberhart & Kennedy 1995 PSO with the standard inertia-weight update:

  v[i,t+1] = w·v[i,t] + c1·r1·(pbest[i] - x[i,t]) + c2·r2·(gbest - x[i,t])
  x[i,t+1] = clamp(x[i,t] + v[i,t+1], bounds)

Single-objective only, `Vec<f64>` decisions only (PSO's velocity vector
needs a Euclidean structure that doesn't generalize cleanly to bool/perm).
Velocities are clamped to ±(hi - lo) per dim to keep particles from
exploding off into space.

Config exposes the four standard knobs — swarm size, generations,
inertia w, cognitive c1, social c2 — plus a seed. Tests cover
convergence on Sphere1D, deterministic reruns, and panic on
multi-objective.

src/algorithms/mod.rs

@@ -8,6 +8,7 @@ pub mod nsga2;
 pub mod nsga3;
 pub mod paes;
 pub(crate) mod parallel_eval;
+pub mod particle_swarm;
 pub mod random_search;
 pub mod simulated_annealing;
 pub mod spea2;
@@ -19,6 +20,7 @@ pub use moead::*;
 pub use nsga2::*;
 pub use nsga3::*;
 pub use paes::*;
+pub use particle_swarm::*;
 pub use random_search::*;
 pub use simulated_annealing::*;
 pub use spea2::*;