feature: add apple silicon native macOS support (#81)

* feature: add apple silicon native macOS support - #81

* (macos): Fix crash

This fixes a crash when viewing the rear camera

* fix(macos): keep interpolated presentation on main thread

* fix(macos): supply Retro-WFC payload during setup

* perf(windows): compile out flat-memory fallback check

* remove duplicate smoke test

* test(macos): name and focus host platform tests

* fix(macos): validate Retro-WFC payload cache

* fix(payload): preserve staged file access failures

* Limit flat-page checks to variable-page hosts

---------

Co-authored-by: patchzyy <64382339+patchzyy@users.noreply.github.com>

runtime/include/guest_flat_memory.h

@@ -14,10 +14,17 @@ namespace GuestFlat {
 // Fixed base so the emitted access is `[reg + imm64-in-register]` with no load
 // of a global.
 inline constexpr uint64_t kGuestSpaceSize = 0x1'0000'0000ull;
+inline constexpr size_t kGuestPageSize = 0x1000;
 #if defined(__x86_64__)
 // 16 TiB: clear of the Windows ASan shadow (32 TiB) and of the usual image/heap
 // placement.
 inline constexpr uintptr_t kFixedFlatGuestBase = 0x0000'1000'0000'0000ull;
+#elif defined(__aarch64__) && defined(__APPLE__)
+// Keep this well above the low address ranges that Darwin's ASLR may use for
+// a PIE executable and its shared cache. Apple Silicon's user VA is wider
+// than Linux's 39-bit minimum, so this 512 GiB region is available while the
+// Linux AArch64 target retains its 64 GiB placement below.
+inline constexpr uintptr_t kFixedFlatGuestBase = 0x0000'0080'0000'0000ull;
 #elif defined(__aarch64__)
 // 16 TiB (this arch's x86_64 sibling value) is unreachable on any AArch64
 // kernel configured for 39-bit virtual addresses (512 GiB ceiling) - common on
@@ -58,6 +65,25 @@ struct FaultCounters {
 // True once the reservation exists and translated code may use the flat path.
 bool IsActive();
 
+// True when a host VM page covers more than one 4 KiB Wii page. In that
+// configuration, guest-view page protection cannot safely represent per-Wii-
+// page MMIO, deferred-read, or executable-write state, so general translated
+// accesses must use the checked Memory::* path.
+// Windows user mode and x86-64 always use a 4 KiB base page, so those builds
+// fold this to a compile-time false: it appears in every flat access and must
+// not become a hot-path load. Only AArch64, where the page size is a kernel
+// configuration (4/16/64 KiB), has to probe it at runtime.
+#if defined(_WIN32) || defined(__x86_64__)
+#define MKW_GUEST_FLAT_FIXED_PAGE_SIZE 1
+#endif
+
+#if defined(MKW_GUEST_FLAT_FIXED_PAGE_SIZE)
+inline constexpr bool RequiresCheckedAccess() noexcept { return false; }
+#else
+extern bool g_requiresCheckedAccess;
+inline bool RequiresCheckedAccess() noexcept { return g_requiresCheckedAccess; }
+#endif
+
 // Reserves the 4 GiB space (once per process) and maps every requested region
 // into both views. Throws std::runtime_error with a precise diagnosis when the
 // reservation, the section objects or a view cannot be created - a silent