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/tests.rs

@@ -1,7 +1,7 @@
 //! Element-level checks: rigid-body modes, constant-strain reproduction (the single-element form
 //! of the patch test), mass and load totals, extrapolation.
 
-use modelcraft_model::ElementKind;
+use fieldcraft_model::ElementKind;
 
 use crate::dense::{Cholesky, Matrix};
 use crate::element::{Formulation, Solid};
@@ -203,7 +203,7 @@ fn bad_input_is_an_error() {
 
 #[test]
 fn section_formulations() {
-    use modelcraft_model::{Formulation as F, Integration};
+    use fieldcraft_model::{Formulation as F, Integration};
     let full = F::default();
     let reduced = F { integration: Integration::Reduced, ..F::default() };
     let im = F { incompatible_modes: true, ..F::default() };