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.

runtime/guest_heap.c

@@ -0,0 +1,26 @@
+#include "guest_heap.h"
+#include <limits.h>
+
+int factorio_guest_heap_init(FactorioGuestHeap *heap, uint8_t *memory,
+                             uint64_t memory_size, uint64_t begin, uint64_t end) {
+  if (!heap || !memory || !begin || begin > end || end > memory_size ||
+      memory_size > SIZE_MAX || begin % 16) return 2;
+  *heap = (FactorioGuestHeap){memory, memory_size, begin, begin, end, 0};
+  return 0;
+}
+
+int factorio_guest_heap_allocate(FactorioGuestHeap *heap, uint64_t size, uint64_t *out) {
+  if (!heap || !out || !heap->memory || !heap->begin || heap->begin % 16 ||
+      heap->cursor < heap->begin || heap->cursor > heap->end ||
+      heap->end > heap->memory_size || heap->memory_size > SIZE_MAX ||
+      heap->allocations == UINT_MAX) return 2;
+  uint64_t padding = (16 - heap->cursor % 16) % 16;
+  if (padding > heap->end - heap->cursor) return 1;
+  uint64_t address = heap->cursor + padding;
+  if (!size) size = 1; /* operator new(0) still returns a distinct allocation. */
+  if (size > heap->end - address) return 1;
+  heap->cursor = address + size;
+  ++heap->allocations;
+  *out = address;
+  return 0;
+}