feat: LiveKit voice session, control channel, transcripts (Phase 2)

- VoiceSession: token->connect with fresh-room retry on timeout, agent
  discovery, agent_ready wait, mic enable/mute, text send over lk.chat
- ControlChannel: outbound set_voice/set_model/get_models/set_mode/
  media_state; inbound agent_ready/models/model_changed/task_event
- TranscriptHandler: transcription segments + transcript topic finals,
  partial/final dedupe per role
- ConversationView/OrbView: status orb, mic/text-mode toggles, composer
- ServerConfig: plain ws:// signaling for private IPs (self-signed TLS
  not injectable into SDK WebSocket); Info.plist local networking

Sources/LiveKit/TranscriptHandler.swift

@@ -0,0 +1,68 @@
+import Foundation
+import LiveKit
+
+struct TranscriptEvent: Equatable, Identifiable {
+    enum Role: String {
+        case user
+        case agent
+    }
+
+    let id: String
+    let role: Role
+    var text: String
+    var isFinal: Bool
+    let timestamp: Date
+}
+
+/// Merges the primary transcription segments (Room delegate) with the
+/// secondary `transcript` data topic (finals only). Dedupe rule: a final for a
+/// role closes any open partial row for that role.
+@MainActor
+final class TranscriptHandler: ObservableObject {
+    @Published private(set) var events: [TranscriptEvent] = []
+
+    func receiveSegment(id: String, role: TranscriptEvent.Role, text: String, isFinal: Bool) {
+        guard !text.isEmpty else { return }
+        upsert(id: id, role: role, text: text, isFinal: isFinal)
+    }
+
+    func receiveDataTranscript(role: TranscriptEvent.Role, text: String) {
+        closePartial(for: role)
+        upsert(id: "final-\(role.rawValue)-\(UUID().uuidString)", role: role, text: text, isFinal: true)
+    }
+
+    func clear() {
+        events.removeAll()
+    }
+
+    private func closePartial(for role: TranscriptEvent.Role) {
+        for index in events.indices where !events[index].isFinal && events[index].role == role {
+            events[index].isFinal = true
+        }
+    }
+
+    private func upsert(id: String, role: TranscriptEvent.Role, text: String, isFinal: Bool) {
+        if let index = events.firstIndex(where: { $0.id == id }) {
+            events[index].text = text
+            events[index].isFinal = isFinal
+        } else {
+            events.append(TranscriptEvent(id: id, role: role, text: text, isFinal: isFinal, timestamp: Date()))
+        }
+    }
+}
+
+extension TranscriptHandler: RoomDelegate {
+    nonisolated func room(_ room: Room, participant: Participant, trackPublication: TrackPublication, didReceiveTranscriptionSegments segments: [TranscriptionSegment]) {
+        let role: TranscriptEvent.Role = participant.isAgent ? .agent : .user
+        let isLocal = participant.identity?.stringValue == room.localParticipant.identity?.stringValue
+        let resolvedRole: TranscriptEvent.Role = isLocal ? .user : role
+        let events = segments.map {
+            TranscriptEvent(id: $0.id, role: resolvedRole, text: $0.text, isFinal: $0.isFinal, timestamp: $0.lastReceivedTime)
+        }
+        Task { @MainActor [weak self] in
+            for event in events {
+                self?.receiveSegment(id: event.id, role: event.role, text: event.text, isFinal: event.isFinal)
+            }
+        }
+    }
+}