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/check_save_prefixes.py

@@ -0,0 +1,67 @@
+"""Exercise arbitrary bounded prefix lengths, outer/nested streaming and guards."""
+import io
+import hashlib
+import json
+import struct
+import subprocess
+import tempfile
+import zipfile
+import zlib
+from pathlib import Path
+
+ROOT = Path(__file__).resolve().parents[1]
+OUT = ROOT / 'build/save-prefix'
+OUT.mkdir(parents=True, exist_ok=True)
+runtime = ROOT / 'third_party/wabt/wasm2c'
+subprocess.run(['xcrun', 'clang', '-O2', '-DWASM_RT_USE_MMAP=0', '-DWASM_RT_MEMCHECK_BOUNDS_CHECK=1',
+    '-I'+str(ROOT/'runtime'), '-I'+str(ROOT/'build/version'), '-I'+str(runtime),
+    str(ROOT/'tests/save_prefix_probe.c'), str(ROOT/'runtime/save_header.c'),
+    str(ROOT/'runtime/version_bridge.c'), str(ROOT/'build/version/factorio_version.c'),
+    str(runtime/'wasm-rt-impl.c'), str(runtime/'wasm-rt-mem-impl.c'), '-lz', '-o', str(OUT/'probe')], check=True)
+
+
+def archive(payload, method, streaming=False):
+    class NonSeeking(io.BytesIO):
+        def seek(self, *args): raise OSError('streaming')
+    output = NonSeeking() if streaming else io.BytesIO()
+    with zipfile.ZipFile(output, 'w', compression=method) as z:
+        z.writestr('fixture/level.dat0', zlib.compress(payload))
+    return output.getvalue()
+
+
+checks = 0
+def probe(data, length, expected, status=0):
+    global checks
+    with tempfile.TemporaryDirectory() as directory:
+        path = Path(directory)/'fixture.zip'
+        path.write_bytes(data)
+        result = subprocess.run([str(OUT/'probe'),str(path),str(length)],capture_output=True,text=True)
+        assert result.returncode == (1 if status else 0), result.stderr
+        report = json.loads(result.stdout)
+        assert report['status'] == status, report
+        assert bytes.fromhex(report['prefix_hex']) == expected
+    checks += 1
+
+
+payload = struct.pack('<4HB',2,0,77,0,0) + bytes(range(256))*300
+for method in (zipfile.ZIP_STORED, zipfile.ZIP_DEFLATED):
+    for streaming in (False, True):
+        data = archive(payload,method,streaming)
+        for length in (1,8,9,10,33,4095,4096,4097,65536,len(payload)):
+            probe(data,length,payload[:length])
+        probe(data,len(payload)+1,b'',6)
+        probe(data,0,b'',7)
+        probe(data,1024*1024+1,b'',7)
+probe(b'invalid',33,b'',2)
+incompressible = struct.pack('<4HB',2,0,77,0,0)
+incompressible += b''.join(hashlib.sha256(i.to_bytes(4,'little')).digest() for i in range(2048))
+for method in (zipfile.ZIP_STORED, zipfile.ZIP_DEFLATED):
+    for streaming in (False,True):
+        data=archive(incompressible,method,streaming)
+        for length in (4097,len(incompressible)):
+            probe(data,length,incompressible[:length])
+over_budget=b''.join(hashlib.sha256(i.to_bytes(4,'little')).digest() for i in range(32768))
+probe(archive(over_budget,zipfile.ZIP_STORED),1024*1024,b'',7)
+print(f'PASS: {checks} bounded prefix cases, exact bytes, output guards and failure atomicity')
+(OUT/'verification.json').write_text(json.dumps({'status':'pass','cases':checks,
+    'scope':'synthetic archives; bounded prefix only'},indent=2)+'\n')