feat: consolidate iOS with API and web preserving history

ios/Sources/LiveKit/TranscriptHistory.swift

@@ -0,0 +1,53 @@
+import Foundation
+
+struct HistoryEntry: Codable, Equatable {
+    let role: String
+    let text: String
+    let timestamp: Date
+}
+
+/// Last 50 final transcript entries persisted as JSON in UserDefaults.
+///
+/// Persistence-only store. The visible transcript is the single canonical
+/// collection owned by `TranscriptHandler.events`; this class provides the
+/// durable snapshot it initializes from and syncs to. It performs no dedupe —
+/// all suppression is source-aware and time-bounded in the handler.
+@MainActor
+final class TranscriptHistory: ObservableObject {
+    @Published private(set) var entries: [HistoryEntry] = []
+
+    static let key = "voice_history_isolated_tests"
+    private let storageKey: String
+    static let maxEntries = 50
+
+    init(origin: String? = nil, userID: String? = nil) {
+        // Length-prefixed parts prevent ambiguous origin/account combinations.
+        storageKey = origin.flatMap { origin in userID.map { "voice_history_v2:\(origin.utf8.count):\(origin):\($0)" } } ?? Self.key
+        if let raw = AppPreferences.store.string(forKey: storageKey),
+           let data = raw.data(using: .utf8),
+           let decoded = try? JSONDecoder().decode([HistoryEntry].self, from: data) {
+            entries = Array(decoded.suffix(Self.maxEntries))
+        }
+    }
+
+    /// Replaces the persisted snapshot with exactly the finals currently in the
+    /// canonical visible collection. Called by `TranscriptHandler` after every
+    /// change so persistence and the UI never diverge. No dedupe is applied here:
+    /// same-source repeats are legitimate entries.
+    func sync(finals: [(role: String, text: String, timestamp: Date)]) {
+        entries = Array(finals.suffix(Self.maxEntries).map {
+            HistoryEntry(role: $0.role, text: $0.text, timestamp: $0.timestamp)
+        })
+        persist()
+    }
+
+    func clear() {
+        entries.removeAll()
+        persist()
+    }
+
+    private func persist() {
+        guard let data = try? JSONEncoder().encode(entries) else { return }
+        AppPreferences.store.set(String(decoding: data, as: UTF8.self), forKey: storageKey)
+    }
+}