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_layout_probe.c

@@ -0,0 +1,29 @@
+#include "save_layout.h"
+#include <inttypes.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+
+int main(int argc,char **argv) {
+  if(argc!=3) return 2;
+  FactorioSaveLayout result;
+  memset(&result,0xa5,sizeof(result));
+  FactorioSaveLayout before=result;
+  int status;
+  size_t needed=0;
+  if(!strcmp(argv[1],"zip")) status=factorio_save_map_header(argv[2],&result);
+  else if(!strcmp(argv[1],"bytes")) {
+    FILE *file=fopen(argv[2],"rb"); if(!file) return 2;
+    uint8_t *bytes=malloc(1024*1024); if(!bytes) return 2;
+    size_t count=fread(bytes,1,1024*1024,file); fclose(file);
+    status=factorio_save_layout_bytes(bytes,count,&result,&needed); free(bytes);
+  } else return 2;
+  if(status && memcmp(&before,&result,sizeof(result))) return 3;
+  printf("{\"status\":%d,\"needed\":%zu",status,needed);
+  if(!status) printf(",\"header_offset\":%zu,\"next_offset\":%zu,\"mod_count\":%u,"
+    "\"tick_fields_hex\":[\"%016" PRIx64 "\",\"%016" PRIx64 "\",\"%016" PRIx64 "\"]",
+    result.header_offset,result.next_offset,result.mod_count,
+    result.header.tick_fields[0],result.header.tick_fields[1],result.header.tick_fields[2]);
+  puts("}");
+  return status ? 1 : 0;
+}