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>

crates/voltex_script/lua/lzio.c

@@ -0,0 +1,68 @@
+/*
+** $Id: lzio.c $
+** Buffered streams
+** See Copyright Notice in lua.h
+*/
+
+#define lzio_c
+#define LUA_CORE
+
+#include "lprefix.h"
+
+
+#include <string.h>
+
+#include "lua.h"
+
+#include "llimits.h"
+#include "lmem.h"
+#include "lstate.h"
+#include "lzio.h"
+
+
+int luaZ_fill (ZIO *z) {
+  size_t size;
+  lua_State *L = z->L;
+  const char *buff;
+  lua_unlock(L);
+  buff = z->reader(L, z->data, &size);
+  lua_lock(L);
+  if (buff == NULL || size == 0)
+    return EOZ;
+  z->n = size - 1;  /* discount char being returned */
+  z->p = buff;
+  return cast_uchar(*(z->p++));
+}
+
+
+void luaZ_init (lua_State *L, ZIO *z, lua_Reader reader, void *data) {
+  z->L = L;
+  z->reader = reader;
+  z->data = data;
+  z->n = 0;
+  z->p = NULL;
+}
+
+
+/* --------------------------------------------------------------- read --- */
+size_t luaZ_read (ZIO *z, void *b, size_t n) {
+  while (n) {
+    size_t m;
+    if (z->n == 0) {  /* no bytes in buffer? */
+      if (luaZ_fill(z) == EOZ)  /* try to read more */
+        return n;  /* no more input; return number of missing bytes */
+      else {
+        z->n++;  /* luaZ_fill consumed first byte; put it back */
+        z->p--;
+      }
+    }
+    m = (n <= z->n) ? n : z->n;  /* min. between n and z->n */
+    memcpy(b, z->p, m);
+    z->n -= m;
+    z->p += m;
+    b = (char *)b + m;
+    n -= m;
+  }
+  return 0;
+}
+