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/Features/Settings/SettingsView.swift

@@ -2,7 +2,15 @@ import SwiftUI
 
 struct SettingsView: View {
     @ObservedObject var settings: SettingsStore
+    var session: VoiceSession?
     @State private var urlText: String = ""
+    @State private var showVoicePicker = false
+    @State private var showModelPicker = false
+
+    init(settings: SettingsStore, session: VoiceSession? = nil) {
+        self.settings = settings
+        self.session = session
+    }
 
     var body: some View {
         Form {
@@ -15,6 +23,26 @@ struct SettingsView: View {
                         settings.serverURL = newValue
                     }
             }
+            Section("Voice") {
+                Button {
+                    showVoicePicker = true
+                } label: {
+                    LabeledContent("Voice", value: Voices.display(for: settings.voiceID) ?? settings.voiceID)
+                }
+            }
+            Section("Model") {
+                if let session, !session.models.isEmpty {
+                    Button {
+                        showModelPicker = true
+                    } label: {
+                        LabeledContent("Model", value: session.selectedModel ?? settings.modelID ?? "—")
+                    }
+                } else {
+                    Text(session != nil ? "Loading available models…" : "Start a conversation to load the model list.")
+                        .font(.footnote)
+                        .foregroundStyle(.secondary)
+                }
+            }
             Section("Interaction") {
                 Toggle("Text mode", isOn: $settings.textMode)
             }
@@ -25,9 +53,97 @@ struct SettingsView: View {
             }
         }
         .navigationTitle("Settings")
+        .sheet(isPresented: $showVoicePicker) {
+            VoicePickerView(settings: settings, session: session)
+        }
+        .sheet(isPresented: $showModelPicker) {
+            ModelPickerView(settings: settings, session: session)
+        }
+    }
+}
+
+struct VoicePickerView: View {
+    @ObservedObject var settings: SettingsStore
+    var session: VoiceSession?
+    @Environment(\.dismiss) private var dismiss
+
+    var body: some View {
+        NavigationStack {
+            List {
+                ForEach(Voices.all, id: \.id) { voice in
+                    Button {
+                        settings.voiceID = voice.id
+                        Task { await session?.selectVoice(voice.id) }
+                        dismiss()
+                    } label: {
+                        HStack {
+                            Text(voice.displayName)
+                            if settings.voiceID == voice.id {
+                                Spacer()
+                                Image(systemName: "checkmark")
+                                    .foregroundStyle(.blue)
+                            }
+                        }
+                    }
+                }
+            }
+            .navigationTitle("Voice")
+            .toolbar {
+                ToolbarItem(placement: .cancellationAction) {
+                    Button("Cancel") { dismiss() }
+                }
+            }
+        }
+    }
+}
+
+struct ModelPickerView: View {
+    @ObservedObject var settings: SettingsStore
+    var session: VoiceSession?
+    @Environment(\.dismiss) private var dismiss
+
+    private var activeModelID: String? {
+        guard let session else { return settings.modelID }
+        if !session.models.isEmpty,
+           let selected = session.selectedModel ?? settings.modelID,
+           session.models.contains(where: { $0.id == selected }) {
+            return selected
+        }
+        return session.models.first?.id
+    }
+
+    var body: some View {
+        NavigationStack {
+            List {
+                ForEach(session?.models ?? [], id: \.id) { model in
+                    Button {
+                        settings.modelID = model.id
+                        Task { await session?.selectModel(model.id) }
+                        dismiss()
+                    } label: {
+                        HStack {
+                            Text(model.name ?? model.id)
+                            if activeModelID == model.id {
+                                Spacer()
+                                Image(systemName: "checkmark")
+                                    .foregroundStyle(.blue)
+                            }
+                        }
+                    }
+                }
+            }
+            .navigationTitle("Model")
+            .toolbar {
+                ToolbarItem(placement: .cancellationAction) {
+                    Button("Cancel") { dismiss() }
+                }
+            }
+        }
     }
 }
 
 #Preview {
-    SettingsView(settings: SettingsStore())
+    NavigationStack {
+        SettingsView(settings: SettingsStore())
+    }
 }