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/tests/host_context_tests.cpp

@@ -0,0 +1,49 @@
+#include "host_context.h"
+
+#include <cstdlib>
+
+namespace {
+// The worker yields twice; each return to the scheduler must preserve both
+// context identities and the worker's continuation point.
+HostContext::Handle g_scheduler = nullptr;
+HostContext::Handle g_worker = nullptr;
+int g_steps = 0;
+
+void Worker(void*)
+{
+    if (!HostContext::IsCurrent(g_worker)) {
+        std::abort();
+    }
+    ++g_steps;
+    HostContext::Switch(g_scheduler);
+    if (!HostContext::IsCurrent(g_worker)) {
+        std::abort();
+    }
+    ++g_steps;
+    HostContext::Switch(g_scheduler);
+}
+} // namespace
+
+int main()
+{
+    if (!HostContext::InitializeScheduler(&g_scheduler) ||
+        !HostContext::IsCurrent(g_scheduler)) {
+        return 1;
+    }
+    g_worker = HostContext::Create(64 * 1024, Worker, nullptr);
+    if (!g_worker) {
+        return 1;
+    }
+
+    HostContext::Switch(g_worker);
+    if (g_steps != 1 || !HostContext::IsCurrent(g_scheduler)) {
+        return 1;
+    }
+    HostContext::Switch(g_worker);
+    if (g_steps != 2 || !HostContext::IsCurrent(g_scheduler)) {
+        return 1;
+    }
+
+    HostContext::Destroy(g_worker);
+    HostContext::ShutdownScheduler(g_scheduler);
+}