Native iPhone port of Factorio 2.0.77

Run the original macOS ARM64 game code on iOS:
- tools/retarget.py: header-only Mach-O retargeting to an iOS dylib
- platform/native: UIKit host and macOS API shims (AppKit for SDL's
  Cocoa backend, CoreGraphics displays, CoreAudio device, Metal device
  properties, Wuffs PNG decoding, Steam and peripheral stubs)
- touch, overlay, iOS keyboard and hardware keyboard input
- tools/build_native.py: build, sign, install, data copy, launch
- docs: build guide, controls, architecture

Also includes the earlier static-translation research (ARM64 -> WASM ->
native) under docs/research, runtime/, tests/ and tools/.

No game files are included; the build reads them from a local install.

tests/save_probe.c

@@ -0,0 +1,11 @@
+#include "save_header.h"
+#include <stdio.h>
+int main(int argc, char **argv) {
+  if (argc != 2) return 64;
+  FactorioMapVersion version;
+  int status = factorio_save_header(argv[1], &version);
+  if (!status) printf("{\"status\":0,\"major\":%u,\"minor\":%u,\"patch\":%u,\"build\":%u,\"flag\":%u}\n",
+    version.major, version.minor, version.patch, version.build, version.flag);
+  else printf("{\"status\":%d}\n", status);
+  return status ? 1 : 0;
+}