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/Conversation/ConversationView.swift

@@ -12,14 +12,16 @@ struct ConversationView: View {
         if case .success(let value) = config {
             _session = StateObject(wrappedValue: VoiceSession(
                 config: value,
-                tokenClient: TokenClient(config: value)
+                tokenClient: TokenClient(config: value),
+                settings: settings
             ))
         } else {
             let fallback = ServerConfig.parse("https://192.168.86.2:9178")
             if case .success(let value) = fallback {
                 _session = StateObject(wrappedValue: VoiceSession(
                     config: value,
-                    tokenClient: TokenClient(config: value)
+                    tokenClient: TokenClient(config: value),
+                    settings: settings
                 ))
             } else {
                 fatalError("Unreachable: default server URL is valid")
@@ -73,6 +75,11 @@ struct ConversationView: View {
                     .font(.caption)
                     .foregroundStyle(.secondary)
             }
+            if session.state == .ready {
+                Text("\(Voices.display(for: settings.voiceID) ?? settings.voiceID) · \(session.selectedModel ?? settings.modelID ?? "—")")
+                    .font(.caption)
+                    .foregroundStyle(.secondary)
+            }
             if session.state == .ready {
                 HStack(spacing: 16) {
                     Toggle(isOn: Binding(
@@ -168,7 +175,7 @@ struct ConversationView: View {
     private var toolbarContent: some ToolbarContent {
         ToolbarItem(placement: .topBarTrailing) {
             NavigationLink {
-                SettingsView(settings: settings)
+                SettingsView(settings: settings, session: session)
             } label: {
                 Image(systemName: "gearshape")
             }