Paramodel — the central algebra crate.
Everything paramodel models lives here: the parameter algebra
(parameter / domain / constraint / value / validation / expression),
the attribute layer (labels, tags, plugs, sockets, wires), the
element model (Element, Dependency, runtime), and the
trial-as-element-parameterization layer (Trial, Assignments).
The crate was formerly split into paramodel-core and
paramodel-elements, with Trial living in paramodel-trials.
That split cost indirection without buying value — Trial is a
specific parameterization of an element graph over specific
coordinates, which puts it in the same semantic unit as Element.
Downstream specialisation (trial sets, outcomes, plans,
compilation, execution) still lives in sibling crates — this one
is the algebra they're built on.