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

tests/oracle/mh-solid-patch/fixture.json

@@ -1,5 +1,5 @@
 {
-  "note": "ModelCraft's accepted results for this case, written by `cargo xtask oracle --bless`. A result outside its band fails CI.",
+  "note": "FieldCraft's accepted results for this case, written by `cargo xtask oracle --bless`. A result outside its band fails CI.",
   "values": {
     "sxx": {
       "band": 2.000000000000001e-6,