ModelCraft foundation: workspace, quality gates, FE model, command engine, geometry boundary

A pure-Rust CAE modeling workspace following the SolidCraft conventions:
- modelcraft-model: nodes and elements by label with hostile-input validation
- modelcraft-geometry: SolidCraft's kernel (pinned git dependency) behind our own API;
  tessellation into a face-tagged boundary surface for volume meshing
- modelcraft-engine: CommandSpec registry, Session::execute with rollback and panic guard,
  scripts and a journal
- modelcraft-cli: list commands, run scripts
- xtask: layers (only geometry may use solidcraft-*), assets, licences, tests, wasm, ci
- AGENTS.md, architecture, ADR 0001 (libraries and licences), roadmap, CI

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

crates/engine/src/cmd/model.rs

@@ -0,0 +1,10 @@
+use serde_json::{Value, json};
+
+use crate::{CommandSpec, Result, Session};
+
+pub const INFO: CommandSpec = CommandSpec { id: "model.info", label: "Model Info", params: "{}", run: info };
+
+fn info(s: &mut Session, _: &Value) -> Result<Value> {
+    let counts: serde_json::Map<String, Value> = s.model.element_counts().into_iter().map(|(k, n)| (k.name().to_string(), json!(n))).collect();
+    Ok(json!({"nodes": s.model.nodes().len(), "elements": counts}))
+}