feat(script): add voltex_script crate with Lua 5.4 FFI and safe wrapper

Compiles Lua 5.4 from source via cc crate (excluding lua.c/luac.c).
Provides ffi bindings, LuaState safe wrapper, and default engine bindings.
All 9 tests pass (exec, globals, register_fn, voltex_print).

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

Cargo.lock

@@ -2107,6 +2107,13 @@ dependencies = [
  "winit",
 ]
 
+[[package]]
+name = "voltex_script"
+version = "0.1.0"
+dependencies = [
+ "cc",
+]
+
 [[package]]
 name = "walkdir"
 version = "2.5.0"