fix: import rand distributions from ndarray_rand::rand_distr to fix E0277 trait-bound

[hyperpolymath]

Why

Both crates/esn/src/lib.rs and crates/lsm/src/lib.rs import Normal, Uniform, Bernoulli from the top-level rand_distr crate, then pass those distribution instances to:

• Array2::random_using(...) from ndarray_rand::RandomExt, which requires ndarray_rand::rand_distr::Distribution
• rng.sample(...) which works fine with either

ndarray-rand re-exports its own pinned version of rand_distr and the RandomExt::random_using trait bound is over that re-exported Distribution. When the top-level rand_distr version drifts (Dependabot bump), it stops being the same type as ndarray_rand::rand_distr::Distribution and the trait bound fails:

error[E0277]: the trait bound `rand_distr::Normal<{float}>: ndarray_rand::rand_distr::Distribution<_>` is not satisfied

…on every Dependabot PR that touched the rand family.

Fix

Import distributions through ndarray_rand::rand_distr so the version always matches the trait bound. No runtime / behaviour change.

Tested

Static: rg confirms Normal/Uniform/Bernoulli are only used through rng.sample() and Array2::random_using(), both of which accept the ndarray_rand::rand_distr versions.

After this lands, the workspace's top-level rand_distr dep may be unused — left in place to avoid scope creep; can drop in a follow-up if cargo-udeps flags it.