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/model/tests/definition.rs

@@ -1,7 +1,7 @@
 //! A whole model definition on a tagged mesh: sets by geometry name survive a remesh, the check
 //! names what is missing, and the model round-trips through JSON.
 
-use modelcraft_model::*;
+use fieldcraft_model::*;
 
 /// A bar of `n` unit hexahedra along X, labels starting after `offset`, tagged as body `Bar` with
 /// faces `left` (x = 0) and `right` (x = n), and the vertex `tip` at (n, 0, 0).