feat(clients): event sound effects + optional text-to-speech

Add audible cues and optional spoken announcements for session events
(join/leave, channel + PM sent/recv, login, logout/connection-lost,
mic on/off, voice-activity, PTT) across all three clients, driven off
the shared C ABI vc_event stream so the mapping stays consistent.

TTS is off by default; when enabled it announces events and reads
message/PM bodies aloud. Master toggles + a sound-volume slider; the
per-utterance voice-activity and PTT cues default off. WAVs ship from
assets/sounds/.

Windows (built + verified): new VoiceCat.App/Notifications/ layer
(FeedbackSettings -> %AppData%\VoiceCat\feedback.json, SoundPlayerPool
via System.Media.SoundPlayer, SpeechAnnouncer via Prismatoid 0.3.0,
EventFeedback dispatcher); MainForm hooks; NotificationSettingsForm
under Settings > Notifications; csproj adds the Prismatoid PackageRef
and copies the WAVs into sounds\.

macOS + iOS (written, not yet built -- needs a Mac): shared
VoiceCatCore/Feedback/ (SoundEvent, EventFeedback = AVAudioPlayer pool
+ native AVSpeechSynthesizer, FeedbackSettings over UserDefaults); WAVs
bundled via Package.swift resources (.process). Hooks in SessionState/
AppState (iOS) and MainWindowController (macOS); settings UI in
SettingsView (iOS) and SettingsWindowController (macOS).

No core/server code touched; ctest --preset dev unaffected.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

clients/apple/iOS/VoiceCatiOS/SessionState.swift

@@ -92,7 +92,22 @@ final class SessionState {
         case .channelList:
             refreshChannels()
             syncSelfChannel()
-        case .userJoined, .userLeft:
+        case .userJoined:
+            // ev.text = nickname, ev.channelId = the channel they joined (per voicecat.h).
+            if ev.userId != selfUserId && ev.channelId == currentChannelId {
+                EventFeedback.shared.play(.channelJoin)
+                EventFeedback.shared.speak("\(ev.text ?? "Someone") joined")
+            }
+            refreshUsers()
+            syncSelfChannel()
+        case .userLeft:
+            // Capture the leaving user's prior nickname/channel before refreshUsers() drops them.
+            if ev.userId != selfUserId,
+               let gone = users.first(where: { $0.id == ev.userId }),
+               gone.channelId == currentChannelId {
+                EventFeedback.shared.play(.channelLeave)
+                EventFeedback.shared.speak("\(gone.nickname) left")
+            }
             refreshUsers()
             syncSelfChannel()
         case .userUpdated:
@@ -103,13 +118,27 @@ final class SessionState {
             }
         case .textMessage:
             let sender = users.first(where: { $0.id == ev.userId })?.nickname ?? "Unknown"
+            let body = ev.text ?? ""
+            let isSelf = ev.userId == selfUserId
+            let isPrivate = ev.textScope == .private
             messages.append(ChatMessage(
                 timestamp: Date(timeIntervalSince1970: Double(ev.timestampUnixMs) / 1000),
                 senderName: sender,
-                text: ev.text ?? "",
+                text: body,
                 scope: ev.textScope))
+            EventFeedback.shared.play(isPrivate
+                ? (isSelf ? .pmSent : .pmRecv)
+                : (isSelf ? .channelSent : .channelRecv))
+            if !isSelf {
+                EventFeedback.shared.speak(isPrivate
+                    ? "Private message from \(sender): \(body)"
+                    : "\(sender): \(body)")
+            }
         case .talkState:
             let talking = ev.u32a != 0
+            if ev.userId == selfUserId {
+                EventFeedback.shared.play(talking ? .vaStart : .vaStop)
+            }
             let who = users.first(where: { $0.id == ev.userId })?.nickname ?? "user \(ev.userId)"
             addActivity(talking ? "\(who) started talking" : "\(who) stopped talking")
         case .streamStarted:
@@ -155,6 +184,10 @@ final class SessionState {
             }
         case .accountList:
             accounts = client.listAccounts()
+        case .disconnected:
+            // Audible cue only — session teardown is driven elsewhere (AppState / UI).
+            EventFeedback.shared.play(ev.result == .ok ? .logout : .connectionLost)
+            EventFeedback.shared.speak(ev.result == .ok ? "Disconnected" : "Connection lost")
         default:
             break
         }
@@ -247,6 +280,7 @@ final class SessionState {
         if result == .ok {
             voiceState.micActive = true
             voiceState.localStreamId = streamId
+            EventFeedback.shared.play(.voiceOn)
             // Publish the active mic stream ID so IOSAudioRouter can reset the core's capture
             // channel count when the user switches mono↔stereo (selectCaptureChannels /
             // applyPreset). Without this, switching stereo→mono leaves the LocalStream's
@@ -291,6 +325,7 @@ final class SessionState {
             client.stopStream(voiceState.localStreamId)
             voiceState.localStreamId = 0
             AudioSessionManager.shared.activeMicStreamId = nil
+            EventFeedback.shared.play(.voiceOff)
         }
         if wasVPIO {
             client.setExternalPlayback(false)
@@ -367,8 +402,12 @@ final class SessionState {
         voiceState.vadThreshold = threshold
     }
 
+    private var pttEngaged = false
     func setPushToTalk(_ active: Bool) {
         client.setPushToTalk(active)
+        // Play the PTT cue only on the press transition (the gesture fires repeatedly while held).
+        if active && !pttEngaged { EventFeedback.shared.play(.ptt) }
+        pttEngaged = active
     }
 
     // MARK: - Text