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.

tools/build_save_layout.py

@@ -0,0 +1,25 @@
+#!/usr/bin/env python3
+"""Build the bounded 2.0.77 envelope adapter and real map-header probe."""
+import subprocess
+from pathlib import Path
+
+ROOT=Path(__file__).resolve().parents[1]
+OUT=ROOT/'build/save-layout'
+OUT.mkdir(parents=True,exist_ok=True)
+RUNTIME=ROOT/'third_party/wabt/wasm2c'
+includes=['-I'+str(p) for p in (ROOT/'runtime',ROOT/'build/version',ROOT/'build/map-header',RUNTIME)]
+flags=['-O2','-DWASM_RT_USE_MMAP=0','-DWASM_RT_MEMCHECK_BOUNDS_CHECK=1']
+sources=[ROOT/'runtime/save_layout.c',ROOT/'runtime/save_header.c',ROOT/'runtime/version_bridge.c',
+         ROOT/'runtime/map_header_bridge.c',ROOT/'build/version/factorio_version.c',
+         ROOT/'build/map-header/factorio_map_header.c',RUNTIME/'wasm-rt-impl.c',RUNTIME/'wasm-rt-mem-impl.c',
+         ROOT/'tests/save_layout_probe.c']
+subprocess.run(['xcrun','clang',*flags,*includes,*map(str,sources),'-lz','-o',str(OUT/'probe')],cwd=ROOT,check=True)
+subprocess.run(['xcrun','clang',*flags,*includes,*map(str,sources[:-1]),
+                str(ROOT/'tests/save_layout_native.c'),str(ROOT/'build/map-header/oracle.S'),
+                '-lz','-o',str(OUT/'verify_native')],cwd=ROOT,check=True)
+sdk=subprocess.check_output(['xcrun','--sdk','iphoneos','--show-sdk-path'],text=True).strip()
+obj=OUT/'save_layout.ios.o'
+subprocess.run(['xcrun','--sdk','iphoneos','clang','-target','arm64-apple-ios15.0','-isysroot',sdk,
+                *flags,*includes,'-c',str(ROOT/'runtime/save_layout.c'),'-o',str(obj)],check=True)
+subprocess.run(['xcrun','libtool','-static','-o',str(OUT/'libfactorio_save_layout_ios.a'),str(obj)],check=True)
+print('Built bounded scenario-envelope adapter and linked AOT constructor probe')