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/App/SettingsStore.swift

@@ -29,7 +29,8 @@ final class SettingsStore: ObservableObject {
     init() {
         let d = UserDefaults.standard
         serverURL = d.string(forKey: Keys.serverURL) ?? "https://192.168.86.2:9178"
-        voiceID = d.string(forKey: Keys.voiceID) ?? ""
+        let storedVoice = d.string(forKey: Keys.voiceID)
+        voiceID = Voices.all.contains { $0.id == storedVoice } ? (storedVoice ?? "") : Voices.defaultID
         modelID = d.string(forKey: Keys.modelID)
         textMode = d.bool(forKey: Keys.textMode)
         volume = d.object(forKey: Keys.volume) as? Double ?? 0.8

Sources/App/Voices.swift

@@ -0,0 +1,34 @@
+import Foundation
+
+struct VoiceOption: Equatable {
+    let id: String
+    let name: String
+    let tag: String?
+
+    var displayName: String {
+        tag.map { "\(name) (\($0))" } ?? name
+    }
+}
+
+enum Voices {
+    static let all: [VoiceOption] = [
+        VoiceOption(id: "en-US-Ava:DragonHDOmniLatestNeural", name: "Ava", tag: "Dragon HD Omni"),
+        VoiceOption(id: "en-US-JennyNeural", name: "Jenny", tag: nil),
+        VoiceOption(id: "en-US-GuyNeural", name: "Guy", tag: nil),
+        VoiceOption(id: "en-US-AndrewNeural", name: "Andrew", tag: nil),
+        VoiceOption(id: "en-US-AriaNeural", name: "Aria", tag: nil),
+        VoiceOption(id: "en-US-EmmaNeural", name: "Emma", tag: nil),
+        VoiceOption(id: "en-US-EricNeural", name: "Eric", tag: nil),
+        VoiceOption(id: "en-US-BrianNeural", name: "Brian", tag: nil),
+        VoiceOption(id: "en-US-AshleyNeural", name: "Ashley", tag: nil),
+        VoiceOption(id: "en-US-RichardNeural", name: "Richard", tag: nil),
+        VoiceOption(id: "en-US-TinaNeural", name: "Tina", tag: nil),
+        VoiceOption(id: "en-US-SteffanNeural", name: "Steffan", tag: nil),
+    ]
+
+    static var defaultID: String { all[0].id }
+
+    static func display(for id: String) -> String? {
+        all.first { $0.id == id }?.displayName
+    }
+}