LS-DYNA keyword writer (implicit static and eigenvalue, M3) (#25)

* decks: LS-DYNA keyword writer (long format, implicit static and eigenvalue)

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01NmAttHhUZTokgPeEJia8sm

* decks: LS-DYNA golden files, Jacobian-sign node-order tests, re-reader and refusals

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01NmAttHhUZTokgPeEJia8sm

* docs: LS-DYNA writer status and deck notes

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01NmAttHhUZTokgPeEJia8sm

* decks: simplify the LS-DYNA writer (plan decides once, cards written in place, shared test tables)

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01NmAttHhUZTokgPeEJia8sm

* decks: LS-DYNA joins FORMATS (deck.write lsdyna), refusals reported together, shared concentrated loads

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01NmAttHhUZTokgPeEJia8sm

* decks: LS-DYNA on main's shared deck API (steps parameter, model helpers)

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01NmAttHhUZTokgPeEJia8sm

---------

Co-authored-by: jyviko <2501648+jyviko@users.noreply.github.com>
Co-authored-by: Claude Opus 5.5 <noreply@anthropic.com>

crates/decks/src/lib.rs

@@ -10,6 +10,7 @@
 #![forbid(unsafe_code)]
 
 pub mod abaqus;
+pub mod lsdyna;
 pub mod nastran;
 
 use std::collections::{BTreeMap, BTreeSet};
@@ -86,6 +87,7 @@ pub fn with_steps(model: &Model, names: &[String]) -> Result<Model> {
 pub const FORMATS: &[Format] = &[
     Format { name: "abaqus", extension: "inp", writer: abaqus::write_resolved },
     Format { name: "nastran", extension: "bdf", writer: nastran::write_resolved },
+    Format { name: "lsdyna", extension: "k", writer: lsdyna::write_resolved },
 ];
 
 /// The format called `name`.