feat: conversation state machine, mic meter, history, wake lock (Phase 3)

Sources/LiveKit/TranscriptHandler.swift

@@ -21,20 +21,30 @@ struct TranscriptEvent: Equatable, Identifiable {
 final class TranscriptHandler: ObservableObject {
     @Published private(set) var events: [TranscriptEvent] = []
 
+    let history = TranscriptHistory()
+
     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)
+        if isFinal {
+            history.add(role: role.rawValue, text: text)
+        }
     }
 
     func receiveDataTranscript(role: TranscriptEvent.Role, text: String) {
         closePartial(for: role)
         upsert(id: "final-\(role.rawValue)-\(UUID().uuidString)", role: role, text: text, isFinal: true)
+        history.add(role: role.rawValue, text: text)
     }
 
     func clear() {
         events.removeAll()
     }
 
+    func clearHistory() {
+        history.clear()
+    }
+
     private func closePartial(for role: TranscriptEvent.Role) {
         for index in events.indices where !events[index].isFinal && events[index].role == role {
             events[index].isFinal = true