feat: voice and model pickers with sync-on-join (Phase 4)

- Voices.swift: 13 Azure voices, default en-US-Ava
- SettingsStore: persist voiceID/modelID, fallback to default voice
- VoiceSession: sync set_voice/set_model on agent_ready, selectVoice/selectModel, track models + model_changed
- SettingsView: voice and model picker sheets
- ControlChannel: publish via publish(data:) reliable data channel instead of sendText DataStream (agent listens on legacy data_received; DataStream text was dropped)

Sources/LiveKit/VoiceSession.swift

@@ -26,6 +26,8 @@ final class VoiceSession: ObservableObject {
     @Published private(set) var agent: AgentInfo?
     @Published private(set) var isMuted = false
     @Published private(set) var micError: String?
+    @Published private(set) var models: [ControlChannel.ModelInfo] = []
+    @Published private(set) var selectedModel: String?
 
     private(set) var room = Room()
     let controlChannel = ControlChannel()
@@ -33,18 +35,40 @@ final class VoiceSession: ObservableObject {
     let stateModel = ConversationStateModel()
     private let config: ServerConfig
     private let tokenClient: TokenClient
+    private let settings: SettingsStore
     private var reconnectAttempted = false
     private var connectAttempts = 0
     private var agentWaitTask: Task<Void, Never>?
 
-    init(config: ServerConfig, tokenClient: TokenClient) {
+    init(config: ServerConfig, tokenClient: TokenClient, settings: SettingsStore) {
         self.config = config
         self.tokenClient = tokenClient
+        self.settings = settings
         room.add(delegate: self)
         room.add(delegate: controlChannel)
         room.add(delegate: transcriptHandler)
-        controlChannel.onEvent = { [weak self] _ in
-            guard self != nil else { return }
+        controlChannel.onEvent = { [weak self] event in
+            Task { @MainActor [weak self] in
+                self?.handleControlEvent(event)
+            }
+        }
+    }
+
+    private func handleControlEvent(_ event: ControlChannel.InboundEvent) {
+        switch event {
+        case .models(let received, let selected):
+            models = received
+            if selectedModel == nil, let selected {
+                selectedModel = selected
+                settings.modelID = selected
+            }
+            logger.log("models received count=\(received.count) selected=\(selected ?? "nil", privacy: .public)")
+        case .modelChanged(let model):
+            selectedModel = model
+            settings.modelID = model
+            logger.log("model_changed applied: \(model, privacy: .public)")
+        default:
+            break
         }
     }
 
@@ -144,6 +168,44 @@ final class VoiceSession: ObservableObject {
         stateModel.start()
         logger.log("state=ready, enabling mic")
         Task { await enableMicrophone() }
+        Task { await syncSettingsOnJoin() }
+    }
+
+    private func syncSettingsOnJoin() async {
+        guard isReady else { return }
+        let voiceID = settings.voiceID
+        do {
+            try await controlChannel.setVoice(voiceID, room: room)
+            logger.log("sync-on-join set_voice sent: \(voiceID, privacy: .public)")
+            if let model = selectedModel ?? settings.modelID {
+                try await controlChannel.setModel(model, room: room)
+                logger.log("sync-on-join set_model sent: \(model, privacy: .public)")
+            }
+        } catch {
+            logger.error("sync-on-join failed: \(String(describing: error), privacy: .public)")
+        }
+    }
+
+    func selectVoice(_ id: String) async {
+        settings.voiceID = id
+        guard isReady else { return }
+        do {
+            try await controlChannel.setVoice(id, room: room)
+            logger.log("set_voice sent: \(id, privacy: .public)")
+        } catch {
+            logger.error("set_voice failed: \(String(describing: error), privacy: .public)")
+        }
+    }
+
+    func selectModel(_ id: String) async {
+        settings.modelID = id
+        guard isReady else { return }
+        do {
+            try await controlChannel.setModel(id, room: room)
+            logger.log("set_model sent: \(id, privacy: .public)")
+        } catch {
+            logger.error("set_model failed: \(String(describing: error), privacy: .public)")
+        }
     }
 
     private func scanForAgent() {
@@ -216,6 +278,7 @@ final class VoiceSession: ObservableObject {
         agent = nil
         isMuted = false
         micError = nil
+        models = []
         reconnectAttempted = false
         stateModel.stop()
         UIApplication.shared.isIdleTimerDisabled = false