engine: parameter schemas for every command

cmd/forms.rs describes each command's parameters: model definitions (sets,
materials with elasticity, plasticity, hyperelasticity, damage, thermal and fluid
options, sections, reference points, couplings, masses, springs, boundary
conditions, loads, fluid domains, steps including nonlinear and explicit),
meshers, solvers, deck export, files and results. Tests check that every command
has a form and that a form's defaults are accepted or refused only for the
required fields left empty.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01UhhZMBTviDQxZvwnyP89fo

crates/engine/src/cmd/mod.rs

@@ -6,6 +6,7 @@ pub(crate) mod deck;
 pub(crate) mod define;
 mod edit;
 pub(crate) mod file;
+pub(crate) mod forms;
 mod geometry;
 mod hex;
 pub(crate) mod mesh;