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/render/src/display.rs

@@ -12,7 +12,7 @@
 //!
 //! The output is deterministic: elements come out in label order, edges sorted.
 
-use modelcraft_model::{ElementKind, Model};
+use fieldcraft_model::{ElementKind, Model};
 
 use crate::{Aabb3, Vec3};
 

crates/render/src/lib.rs

@@ -1,4 +1,4 @@
-//! Display data for ModelCraft, with no GPU dependency: what a finite element model looks like
+//! Display data for FieldCraft, with no GPU dependency: what a finite element model looks like
 //! on screen ([`DisplayMesh`]: the visible faces, element edges, line elements and nodes), an
 //! orbit camera with perspective or orthographic projection, and a CPU rasterizer for headless
 //! snapshots. The desktop viewport draws the same [`Scene`] on the GPU.