better runtime checking of inits

[beckermr]

We should probably use equinox to do better runtime checking of values. For example, if you seed a Poisson deviate with a negative mean, the RNG returns -1 with every call.

In [6]: pd()
Out[6]: Array(-1., dtype=float32)

In [7]: pd()
Out[7]: Array(-1., dtype=float32)

In [8]: pd()
Out[8]: Array(-1., dtype=float32)

In [9]: pd()
Out[9]: Array(-1., dtype=float32)

[ismael-mendoza]

that seems like a good idea and it doesn't seem too hard to make it work using this: https://docs.kidger.site/equinox/api/errors/#equinox.error_if