Add ChatViewModel testability and unit tests

- Add testable ChatViewModel initializer accepting Transport dependency
- Create MockTransport implementing full Transport protocol for testing
- Add 21 unit tests covering:
  - Initialization (delegate, services, nickname)
  - Message sending (basic, empty, mentions, commands)
  - Message receiving (delegate calls, public messages)
  - Peer connections (connect, disconnect, isPeerConnected)
  - Deduplication service integration
  - Private chat routing
  - Bluetooth state handling
  - Panic clear functionality
- Guard NotificationService methods against test environment crashes
- Make deduplicationService internal for test access

All 303 tests pass.

bitchatTests/Mocks/MockTransport.swift

@@ -0,0 +1,228 @@
+//
+// MockTransport.swift
+// bitchatTests
+//
+// Mock Transport implementation for unit testing ChatViewModel.
+// This is free and unencumbered software released into the public domain.
+//
+
+import Foundation
+import Combine
+import CoreBluetooth
+@testable import bitchat
+
+/// Mock Transport implementation for testing ChatViewModel in isolation.
+/// Records all method calls and allows test code to verify interactions.
+final class MockTransport: Transport {
+
+    // MARK: - Protocol Properties
+
+    weak var delegate: BitchatDelegate?
+    weak var peerEventsDelegate: TransportPeerEventsDelegate?
+
+    var myPeerID: PeerID = PeerID(str: "TESTPEER")
+    var myNickname: String = "TestUser"
+
+    private let peerSnapshotSubject = CurrentValueSubject<[TransportPeerSnapshot], Never>([])
+    var peerSnapshotPublisher: AnyPublisher<[TransportPeerSnapshot], Never> {
+        peerSnapshotSubject.eraseToAnyPublisher()
+    }
+
+    // MARK: - Recording Properties (for test assertions)
+
+    private(set) var sentMessages: [(content: String, mentions: [String], messageID: String?, timestamp: Date?)] = []
+    private(set) var sentPrivateMessages: [(content: String, peerID: PeerID, recipientNickname: String, messageID: String)] = []
+    private(set) var sentReadReceipts: [(receipt: ReadReceipt, peerID: PeerID)] = []
+    private(set) var sentDeliveryAcks: [(messageID: String, peerID: PeerID)] = []
+    private(set) var sentFavoriteNotifications: [(peerID: PeerID, isFavorite: Bool)] = []
+    private(set) var sentVerifyChallenges: [(peerID: PeerID, noiseKeyHex: String, nonceA: Data)] = []
+    private(set) var sentVerifyResponses: [(peerID: PeerID, noiseKeyHex: String, nonceA: Data)] = []
+    private(set) var startServicesCallCount = 0
+    private(set) var stopServicesCallCount = 0
+    private(set) var emergencyDisconnectCallCount = 0
+    private(set) var broadcastAnnounceCallCount = 0
+    private(set) var triggeredHandshakes: [PeerID] = []
+
+    // MARK: - Configurable Mock State
+
+    var connectedPeers: Set<PeerID> = []
+    var reachablePeers: Set<PeerID> = []
+    var peerNicknames: [PeerID: String] = [:]
+    var peerFingerprints: [PeerID: String] = [:]
+    var peerNoiseStates: [PeerID: LazyHandshakeState] = [:]
+    private let mockKeychain = MockKeychain()
+
+    // MARK: - Transport Protocol Implementation
+
+    func currentPeerSnapshots() -> [TransportPeerSnapshot] {
+        peerSnapshotSubject.value
+    }
+
+    func setNickname(_ nickname: String) {
+        myNickname = nickname
+    }
+
+    func startServices() {
+        startServicesCallCount += 1
+    }
+
+    func stopServices() {
+        stopServicesCallCount += 1
+    }
+
+    func emergencyDisconnectAll() {
+        emergencyDisconnectCallCount += 1
+        connectedPeers.removeAll()
+        reachablePeers.removeAll()
+    }
+
+    func isPeerConnected(_ peerID: PeerID) -> Bool {
+        connectedPeers.contains(peerID)
+    }
+
+    func isPeerReachable(_ peerID: PeerID) -> Bool {
+        reachablePeers.contains(peerID) || connectedPeers.contains(peerID)
+    }
+
+    func peerNickname(peerID: PeerID) -> String? {
+        peerNicknames[peerID]
+    }
+
+    func getPeerNicknames() -> [PeerID: String] {
+        peerNicknames
+    }
+
+    func getFingerprint(for peerID: PeerID) -> String? {
+        peerFingerprints[peerID]
+    }
+
+    func getNoiseSessionState(for peerID: PeerID) -> LazyHandshakeState {
+        peerNoiseStates[peerID] ?? .none
+    }
+
+    func triggerHandshake(with peerID: PeerID) {
+        triggeredHandshakes.append(peerID)
+    }
+
+    func getNoiseService() -> NoiseEncryptionService {
+        NoiseEncryptionService(keychain: mockKeychain)
+    }
+
+    // MARK: - Messaging
+
+    func sendMessage(_ content: String, mentions: [String]) {
+        sentMessages.append((content, mentions, nil, nil))
+    }
+
+    func sendMessage(_ content: String, mentions: [String], messageID: String, timestamp: Date) {
+        sentMessages.append((content, mentions, messageID, timestamp))
+    }
+
+    func sendPrivateMessage(_ content: String, to peerID: PeerID, recipientNickname: String, messageID: String) {
+        sentPrivateMessages.append((content, peerID, recipientNickname, messageID))
+    }
+
+    func sendReadReceipt(_ receipt: ReadReceipt, to peerID: PeerID) {
+        sentReadReceipts.append((receipt, peerID))
+    }
+
+    func sendFavoriteNotification(to peerID: PeerID, isFavorite: Bool) {
+        sentFavoriteNotifications.append((peerID, isFavorite))
+    }
+
+    func sendBroadcastAnnounce() {
+        broadcastAnnounceCallCount += 1
+    }
+
+    func sendDeliveryAck(for messageID: String, to peerID: PeerID) {
+        sentDeliveryAcks.append((messageID, peerID))
+    }
+
+    func sendFileBroadcast(_ packet: BitchatFilePacket, transferId: String) {
+        // Not tracked for current tests
+    }
+
+    func sendFilePrivate(_ packet: BitchatFilePacket, to peerID: PeerID, transferId: String) {
+        // Not tracked for current tests
+    }
+
+    func cancelTransfer(_ transferId: String) {
+        // Not tracked for current tests
+    }
+
+    func sendVerifyChallenge(to peerID: PeerID, noiseKeyHex: String, nonceA: Data) {
+        sentVerifyChallenges.append((peerID, noiseKeyHex, nonceA))
+    }
+
+    func sendVerifyResponse(to peerID: PeerID, noiseKeyHex: String, nonceA: Data) {
+        sentVerifyResponses.append((peerID, noiseKeyHex, nonceA))
+    }
+
+    // MARK: - Test Helpers
+
+    /// Clears all recorded method calls for fresh assertions
+    func resetRecordings() {
+        sentMessages.removeAll()
+        sentPrivateMessages.removeAll()
+        sentReadReceipts.removeAll()
+        sentDeliveryAcks.removeAll()
+        sentFavoriteNotifications.removeAll()
+        sentVerifyChallenges.removeAll()
+        sentVerifyResponses.removeAll()
+        startServicesCallCount = 0
+        stopServicesCallCount = 0
+        emergencyDisconnectCallCount = 0
+        broadcastAnnounceCallCount = 0
+        triggeredHandshakes.removeAll()
+    }
+
+    /// Simulates a peer connecting
+    func simulateConnect(_ peerID: PeerID, nickname: String? = nil) {
+        connectedPeers.insert(peerID)
+        if let nickname = nickname {
+            peerNicknames[peerID] = nickname
+        }
+        delegate?.didConnectToPeer(peerID)
+        delegate?.didUpdatePeerList(Array(connectedPeers))
+    }
+
+    /// Simulates a peer disconnecting
+    func simulateDisconnect(_ peerID: PeerID) {
+        connectedPeers.remove(peerID)
+        peerNicknames.removeValue(forKey: peerID)
+        delegate?.didDisconnectFromPeer(peerID)
+        delegate?.didUpdatePeerList(Array(connectedPeers))
+    }
+
+    /// Simulates receiving a message
+    func simulateIncomingMessage(_ message: BitchatMessage) {
+        delegate?.didReceiveMessage(message)
+    }
+
+    /// Simulates receiving a public message
+    func simulateIncomingPublicMessage(
+        from peerID: PeerID,
+        nickname: String,
+        content: String,
+        timestamp: Date = Date(),
+        messageID: String? = nil
+    ) {
+        delegate?.didReceivePublicMessage(
+            from: peerID,
+            nickname: nickname,
+            content: content,
+            timestamp: timestamp,
+            messageID: messageID
+        )
+    }
+
+    /// Simulates Bluetooth state change
+    func simulateBluetoothStateChange(_ state: CBManagerState) {
+        delegate?.didUpdateBluetoothState(state)
+    }
+
+    /// Updates the peer snapshot publisher
+    func updatePeerSnapshots(_ snapshots: [TransportPeerSnapshot]) {
+        peerSnapshotSubject.send(snapshots)
+    }
+}