[fix] use VideoToolbox exclusively for iOS H.264

apps/ios/CrossDeskMobile/Bridge/CrossDeskRTCBridge.h

@@ -100,7 +100,6 @@ typedef NS_ENUM(NSInteger, CrossDeskVideoAdaptationPolicy) {
 
 - (void)configureWithSignalHost:(NSString *)host
                      signalPort:(NSInteger)signalPort;
-- (void)setHardwareAccelerationEnabled:(BOOL)enabled;
 - (void)setVideoAdaptationPolicy:(CrossDeskVideoAdaptationPolicy)policy;
 - (void)requestPresenceForRemoteIDs:(NSArray<NSString *> *)remoteIDs
                          subscribe:(BOOL)subscribe

apps/ios/CrossDeskMobile/Bridge/CrossDeskRTCBridge.mm

@@ -75,7 +75,6 @@ struct RTCState {
   CallbackContext controller_context;
   std::string signal_host;
   int signal_port = 0;
-  bool hardware_acceleration = true;
   VideoDegradationPreference video_adaptation_policy =
       VideoDegradationPreference::MaintainResolution;
   bool identity_ready = false;
@@ -332,7 +331,8 @@ Params MakeParams(const RTCState &state, const std::string &user_id,
               state.signal_host);
   params.signal_server_port = state.signal_port;
   CopyCString(params.log_path, sizeof(params.log_path), state.log_path);
-  params.hardware_acceleration = state.hardware_acceleration;
+  // iOS H.264 is provided exclusively by VideoToolbox.
+  params.hardware_acceleration = true;
   params.native_video_output = true;
   params.av1_encoding = false;
   params.turn_mode = TurnMode::TurnAutoUdpTcp;
@@ -495,12 +495,6 @@ Params MakeParams(const RTCState &state, const std::string &user_id,
   });
 }
 
-- (void)setHardwareAccelerationEnabled:(BOOL)enabled {
-  dispatch_async(_rtcQueue, ^{
-    self->_state->hardware_acceleration = enabled;
-  });
-}
-
 - (void)setVideoAdaptationPolicy:(CrossDeskVideoAdaptationPolicy)policy {
   dispatch_async(_rtcQueue, ^{
     switch (policy) {

apps/ios/CrossDeskMobile/ContentView.swift

@@ -686,22 +686,6 @@ private struct ServerSettingsView: View {
                         .font(.footnote)
                         .foregroundStyle(.secondary)
                 }
-                Section("视频编解码") {
-                    Picker("处理方式", selection: $session.videoCodecMode) {
-                        ForEach(VideoCodecMode.allCases) { mode in
-                            Text(mode.title).tag(mode)
-                        }
-                    }
-                    .pickerStyle(.segmented)
-
-                    Text(session.videoCodecMode.detail)
-                        .font(.footnote)
-                        .foregroundStyle(.secondary)
-
-                    Text("修改后从下一次连接开始生效。")
-                        .font(.caption)
-                        .foregroundStyle(.tertiary)
-                }
                 Section("画面偏好") {
                     Picker("偏好模式", selection: $session.videoAdaptationPolicy) {
                         ForEach(VideoAdaptationPolicy.allCases) { policy in

apps/ios/CrossDeskMobile/RemoteSessionModel.swift

@@ -42,43 +42,6 @@ enum MouseControlMode: String, CaseIterable, Identifiable {
     }
 }
 
-enum VideoCodecMode: String, CaseIterable, Identifiable {
-    case hardware
-    case software
-
-    private static let defaultsKey = "crossdesk.mobile.video-codec-mode"
-
-    var id: String { rawValue }
-
-    var title: String {
-        switch self {
-        case .hardware: return "硬件"
-        case .software: return "软件"
-        }
-    }
-
-    var detail: String {
-        switch self {
-        case .hardware:
-            return "使用 VideoToolbox，延迟和耗电更低，推荐日常使用。"
-        case .software:
-            return "使用 OpenH264 软件编解码，适合兼容性测试。"
-        }
-    }
-
-    static var saved: VideoCodecMode {
-        guard let rawValue = UserDefaults.standard.string(forKey: defaultsKey),
-              let mode = VideoCodecMode(rawValue: rawValue) else {
-            return .hardware
-        }
-        return mode
-    }
-
-    func save() {
-        UserDefaults.standard.set(rawValue, forKey: Self.defaultsKey)
-    }
-}
-
 enum VideoAdaptationPolicy: String, CaseIterable, Identifiable {
     case frameRatePriority
     case qualityPriority
@@ -361,9 +324,6 @@ final class RemoteSessionModel: NSObject, ObservableObject, CrossDeskRTCBridgeDe
     @Published var mouseControlMode = MouseControlMode.saved {
         didSet { mouseControlMode.save() }
     }
-    @Published var videoCodecMode = VideoCodecMode.saved {
-        didSet { videoCodecMode.save() }
-    }
     @Published var videoAdaptationPolicy = VideoAdaptationPolicy.saved {
         didSet { videoAdaptationPolicy.save() }
     }
@@ -467,7 +427,6 @@ final class RemoteSessionModel: NSObject, ObservableObject, CrossDeskRTCBridgeDe
         } else if signalConnected {
             signalStatus = "已连接服务器"
         }
-        bridge.setHardwareAccelerationEnabled(videoCodecMode == .hardware)
         bridge.setVideoAdaptationPolicy(videoAdaptationPolicy.bridgeValue)
         bridge.configure(withSignalHost: host,
                          signalPort: signal)