Rename the project to FieldCraft

Crates fieldcraft-*, binaries fieldcraft and fieldcraft-cli, the .fieldcraft file (format tag
fieldcraft/1, manifest fieldcraft.json), FIELDCRAFT_* environment variables, the MCP server
name, egui widget ids (fc_*), the app icon document FieldCraft.icon and its generated family,
docs and licences. No compatibility shim: no files of the earlier name exist.

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

crates/fem/src/plasticity.rs

@@ -36,7 +36,7 @@
 //! Stress 6-vectors hold tensor components (xx, yy, zz, xy, xz, yz), strain increments
 //! engineering shears.
 
-use modelcraft_model::{Damage, Elastic, Hardening, Plastic};
+use fieldcraft_model::{Damage, Elastic, Hardening, Plastic};
 
 use crate::material::von_mises;
 use crate::{Error, Result};
@@ -328,7 +328,7 @@ impl J2 {
 #[cfg(test)]
 mod tests {
     use super::*;
-    use modelcraft_model::HardeningPoint;
+    use fieldcraft_model::HardeningPoint;
 
     const E: f64 = 200_000.0;
     const NU: f64 = 0.3;