feat(ios): ship iOS SwiftUI client (VoiceCatiOS)

Full SwiftUI app at clients/apple/iOS/VoiceCatiOS.xcodeproj:
- 24 Swift source files: AppState + SessionState (@Observable @MainActor),
  AudioSessionManager (AVAudioSession owner + interruption/route handling),
  ServerListStore/SavedServer (App Group container + Keychain sharing),
  and 14 SwiftUI views covering the full feature set
- NavigationSplitView on iPad, TabView on iPhone (horizontalSizeClass)
- Channel tree via OutlineGroup, user list with context menu admin actions
- PTT via DragGesture(minimumDistance: 0) + @GestureState
- onEvent closures hop to MainActor via Task { @MainActor in ... }
- App Group: group.cat.voice.VoiceCat (shared with future ReplayKit extension)

C ABI: add vc_audio_suspend / vc_audio_resume (AudioEngine::suspend/resume)
called by AudioSessionManager on AVAudioSession interruption events.

XCFramework: add ios-arm64 and ios-arm64-simulator slices to build-xcframework.sh;
Package.swift gains .iOS(.v17) platform; CMakePresets.json adds apple-ios /
apple-ios-sim presets with arm64-ios / arm64-ios-simulator vcpkg triplets.

Verified: xcodebuild -target VoiceCatiOS -sdk iphonesimulator26.5 BUILD SUCCEEDED.

core/src/audio/audio_engine.cpp

@@ -274,6 +274,30 @@ void AudioEngine::stop() {
 #endif
 }
 
+bool AudioEngine::suspend() {
+#ifdef VOICECAT_HAS_AUDIO
+    if (!running_.load(std::memory_order_acquire)) return true;
+    bool ok = true;
+    if (capture_started_)  ok &= (ma_device_stop(&capture_device_)  == MA_SUCCESS);
+    if (playback_started_) ok &= (ma_device_stop(&playback_device_) == MA_SUCCESS);
+    return ok;
+#else
+    return true;
+#endif
+}
+
+bool AudioEngine::resume() {
+#ifdef VOICECAT_HAS_AUDIO
+    if (!running_.load(std::memory_order_acquire)) return true;
+    bool ok = true;
+    if (capture_started_)  ok &= (ma_device_start(&capture_device_)  == MA_SUCCESS);
+    if (playback_started_) ok &= (ma_device_start(&playback_device_) == MA_SUCCESS);
+    return ok;
+#else
+    return true;
+#endif
+}
+
 void AudioEngine::inject_capture(int kind, const int16_t* pcm, size_t n) {
     InjectTap* tap;
     {

core/src/audio/audio_engine.h

@@ -127,6 +127,12 @@ class AudioEngine {
 
     bool running() const { return running_.load(std::memory_order_acquire); }
 
+    // Pause/resume miniaudio device I/O (called from vc_audio_suspend/resume for
+    // AVAudioSession interruptions on iOS). Thread-safe via ma_device_stop/start.
+    // Returns true on success; false if a device stop/start fails.
+    bool suspend();
+    bool resume();
+
     // Enumerate input or output devices (for UI pickers / vc_list_devices). Static: works
     // before any AudioEngine instance is running (device pickers need to populate pre-connect).
     // Inits a throwaway ma_context if VOICECAT_HAS_AUDIO; returns {} otherwise. See DeviceInfo

core/src/core/client.cpp

@@ -1399,6 +1399,14 @@ vc_result vc_client::get_remote_stream(uint32_t user_id, uint32_t stream_id,
     return VC_OK;
 }
 
+vc_result vc_client::audio_suspend() {
+    return audio_engine_.suspend() ? VC_OK : VC_ERR_AUDIO;
+}
+
+vc_result vc_client::audio_resume() {
+    return audio_engine_.resume() ? VC_OK : VC_ERR_AUDIO;
+}
+
 vc_result vc_client::get_stream_audio_config(uint32_t user_id, uint32_t stream_id,
                                              vc_audio_config* out) {
     if (state_net_.load(std::memory_order_acquire) != VC_STATE_CONNECTED) return VC_ERR_NOT_CONNECTED;
@@ -1863,5 +1871,7 @@ vc_result vc_client::delete_account(const char*) { return VC_ERR_NOT_IMPLEMENTED
 vc_result vc_client::list_accounts() { return VC_ERR_NOT_IMPLEMENTED; }
 vc_result vc_client::get_account_list(vc_account_list*) { return VC_ERR_NOT_IMPLEMENTED; }
 vc_result vc_client::get_permissions(vc_permissions*) { return VC_ERR_NOT_IMPLEMENTED; }
+vc_result vc_client::audio_suspend() { return VC_ERR_NOT_IMPLEMENTED; }
+vc_result vc_client::audio_resume()  { return VC_ERR_NOT_IMPLEMENTED; }
 
 #endif  // VOICECAT_HAS_NET

core/src/core/client.h

@@ -57,6 +57,8 @@ struct vc_client {
                                 bool noise_reduction);
     vc_result get_remote_stream(uint32_t user_id, uint32_t stream_id,
                                 vc_remote_stream_state* out);
+    vc_result audio_suspend();
+    vc_result audio_resume();
 
     vc_result send_text(vc_text_scope scope, uint32_t target_id, const char* utf8);
 

core/src/voicecat.cpp

@@ -295,4 +295,14 @@ vc_result vc_get_permissions(vc_client* c, vc_permissions* out) {
     return c->get_permissions(out);
 }
 
+vc_result vc_audio_suspend(vc_client* c) {
+    if (c == nullptr) return VC_ERR_INVALID_ARG;
+    return c->audio_suspend();
+}
+
+vc_result vc_audio_resume(vc_client* c) {
+    if (c == nullptr) return VC_ERR_INVALID_ARG;
+    return c->audio_resume();
+}
+
 }  // extern "C"