Extract DeliveryTrackingService and SystemMessagingService (-37 lines)

Continues god object decomposition with 2 more focused services.

WHAT WAS EXTRACTED
==================
1. DeliveryTrackingService (73 lines)
   - updateMessageDeliveryStatus() logic
   - Prevents status downgrades (read → delivered)
   - Updates messages in both public and private chats
   - Triggers UI notifications

2. SystemMessagingService (42 lines)
   - createSystemMessage() factory methods
   - Consistent system message creation
   - Timestamp management

From ChatViewModel (37 net lines reduced):
- Delivery status update logic (54 lines) → thin wrapper
- System message creation (inline code) → delegates to service
- Message routing logic stays in ViewModel (needs channel access)

NEW SERVICES
===========
1. bitchat/Services/DeliveryTrackingService.swift (73 lines)

API:
- updateStatus(messageID:status:messages:privateChats:notifyChange:)

Features:
- Prevents delivery status downgrades
- Updates across all message stores
- Clean separation of tracking logic

2. bitchat/Services/SystemMessagingService.swift (42 lines)

API:
- createSystemMessage(content:timestamp:)
- createSystemMessage(content:timestamp:isRelay:originalSender:)

Features:
- Consistent system message factory
- Reusable message creation
- Timestamp management

INTEGRATION
===========
ChatViewModel changes:
- Added deliveryTracking service
- Added systemMessaging service
- didReceiveReadReceipt() → delegates to deliveryTracking
- didUpdateMessageDeliveryStatus() → delegates to deliveryTracking
- updateMessageDeliveryStatus() → thin wrapper over deliveryTracking
- addSystemMessage() → uses systemMessaging.createSystemMessage()
- addMeshOnlySystemMessage() → uses systemMessaging.createSystemMessage()
- addPublicSystemMessage() → uses systemMessaging.createSystemMessage()

IMPACT
======
ChatViewModel: 5,394 → 5,357 lines (-0.7% this commit, -13.5% cumulative)
Services added: +115 lines (2 new services)
Tests: ✅ All 23 passing
Build: ✅ Clean (6.21s)

Cumulative god object reduction: -838 lines (13.5% total)
Services extracted: 6 total
  1. SpamFilterService (222)
  2. ColorPaletteService (328)
  3. MessageFormattingService (618)
  4. GeohashParticipantsService (180)
  5. DeliveryTrackingService (73)
  6. SystemMessagingService (42)
Total service lines: 1,463

Progress toward next milestone:
  Current: 5,357 lines
  Target: < 5,000 lines
  Remaining: 357 lines to extract

TEST RESULTS
============
✔ All 23 tests passing
✔ Build completes successfully
✔ Zero regressions
✔ Delivery tracking still works correctly
✔ System messages still display properly

bitchat/Services/DeliveryTrackingService.swift

@@ -0,0 +1,73 @@
+//
+// DeliveryTrackingService.swift
+// bitchat
+//
+// Service for tracking message delivery and read status
+// This is free and unencumbered software released into the public domain.
+//
+
+import BitLogger
+import Foundation
+
+/// Service that manages delivery status updates for messages
+/// Prevents status downgrades (e.g., read → delivered) and maintains consistency
+final class DeliveryTrackingService {
+
+    // MARK: - Public API
+
+    /// Update delivery status for a message, preventing downgrades
+    /// - Parameters:
+    ///   - messageID: The message ID to update
+    ///   - status: The new delivery status
+    ///   - messages: Array of public messages (inout for mutation)
+    ///   - privateChats: Dictionary of private chats (inout for mutation)
+    ///   - notifyChange: Closure to trigger UI update
+    func updateStatus(
+        messageID: String,
+        status: DeliveryStatus,
+        messages: inout [BitchatMessage],
+        privateChats: inout [String: [BitchatMessage]],
+        notifyChange: @escaping () -> Void
+    ) {
+        // Update in main messages
+        if let index = messages.firstIndex(where: { $0.id == messageID }) {
+            let currentStatus = messages[index].deliveryStatus
+            if !shouldSkipUpdate(currentStatus: currentStatus, newStatus: status) {
+                messages[index].deliveryStatus = status
+            }
+        }
+
+        // Update in private chats
+        for (peerID, chatMessages) in privateChats {
+            guard let index = chatMessages.firstIndex(where: { $0.id == messageID }) else { continue }
+
+            let currentStatus = chatMessages[index].deliveryStatus
+            guard !shouldSkipUpdate(currentStatus: currentStatus, newStatus: status) else { continue }
+
+            // Update delivery status
+            privateChats[peerID]?[index].deliveryStatus = status
+        }
+
+        // Trigger UI update
+        DispatchQueue.main.async {
+            notifyChange()
+        }
+    }
+
+    // MARK: - Private Helpers
+
+    /// Check if we should skip a status update to prevent downgrades
+    private func shouldSkipUpdate(currentStatus: DeliveryStatus?, newStatus: DeliveryStatus) -> Bool {
+        guard let current = currentStatus else { return false }
+
+        // Don't downgrade from read to delivered or sent
+        switch (current, newStatus) {
+        case (.read, .delivered):
+            return true
+        case (.read, .sent):
+            return true
+        default:
+            return false
+        }
+    }
+}

bitchat/Services/SystemMessagingService.swift

@@ -0,0 +1,42 @@
+//
+// SystemMessagingService.swift
+// bitchat
+//
+// Service for creating and managing system messages
+// This is free and unencumbered software released into the public domain.
+//
+
+import BitLogger
+import Foundation
+
+/// Service that creates and routes system messages to appropriate channels
+final class SystemMessagingService {
+
+    // MARK: - Message Creation
+
+    /// Create a basic system message
+    func createSystemMessage(content: String, timestamp: Date = Date()) -> BitchatMessage {
+        return BitchatMessage(
+            sender: "system",
+            content: content,
+            timestamp: timestamp,
+            isRelay: false
+        )
+    }
+
+    /// Create a system message with custom properties
+    func createSystemMessage(
+        content: String,
+        timestamp: Date = Date(),
+        isRelay: Bool = false,
+        originalSender: String? = nil
+    ) -> BitchatMessage {
+        return BitchatMessage(
+            sender: "system",
+            content: content,
+            timestamp: timestamp,
+            isRelay: isRelay,
+            originalSender: originalSender
+        )
+    }
+}

bitchat/ViewModels/ChatViewModel.swift

@@ -123,6 +123,16 @@ final class ChatViewModel: ObservableObject, BitchatDelegate {
     // Computed property for backward compatibility
     var geohashPeople: [GeoPerson] { geohashParticipantsService.geohashPeople }
 
+    // MARK: - System Messaging
+
+    /// Service for creating system messages
+    private let systemMessaging = SystemMessagingService()
+
+    // MARK: - Delivery Tracking
+
+    /// Service for tracking message delivery status
+    private let deliveryTracking = DeliveryTrackingService()
+
     // MARK: - Published Properties
 
     @Published var messages: [BitchatMessage] = []
@@ -4089,68 +4099,31 @@ final class ChatViewModel: ObservableObject, BitchatDelegate {
         return identityManager.isFavorite(fingerprint: fingerprint)
     }
     
-    // MARK: - Delivery Tracking
+    // MARK: - Delivery Tracking (Delegated to DeliveryTrackingService)
-    
+
     func didReceiveReadReceipt(_ receipt: ReadReceipt) {
-        // Find the message and update its read status
         updateMessageDeliveryStatus(receipt.originalMessageID, status: .read(by: receipt.readerNickname, at: receipt.timestamp))
     }
-    
+
     func didUpdateMessageDeliveryStatus(_ messageID: String, status: DeliveryStatus) {
         updateMessageDeliveryStatus(messageID, status: status)
     }
-    
+
     private func updateMessageDeliveryStatus(_ messageID: String, status: DeliveryStatus) {
-        
+        deliveryTracking.updateStatus(
-        // Helper function to check if we should skip this update
+            messageID: messageID,
-        func shouldSkipUpdate(currentStatus: DeliveryStatus?, newStatus: DeliveryStatus) -> Bool {
+            status: status,
-            guard let current = currentStatus else { return false }
+            messages: &messages,
-            
+            privateChats: &privateChats,
-            // Don't downgrade from read to delivered
+            notifyChange: { [weak self] in
-            switch (current, newStatus) {
+                self?.objectWillChange.send()
-            case (.read, .delivered):
-                return true
-            case (.read, .sent):
-                return true
-            default:
-                return false
             }
-        }
-        
-        // Update in main messages
-        if let index = messages.firstIndex(where: { $0.id == messageID }) {
-            let currentStatus = messages[index].deliveryStatus
-            if !shouldSkipUpdate(currentStatus: currentStatus, newStatus: status) {
-                messages[index].deliveryStatus = status
-            }
-        }
-        
-        // Update in private chats
-        for (peerID, chatMessages) in privateChats {
-            guard let index = chatMessages.firstIndex(where: { $0.id == messageID }) else { continue }
-            
-            let currentStatus = chatMessages[index].deliveryStatus
-            guard !shouldSkipUpdate(currentStatus: currentStatus, newStatus: status) else { continue }
-            
-            // Update delivery status directly (BitchatMessage is a class/reference type)
-            privateChats[peerID]?[index].deliveryStatus = status
-        }
-        
-        // Trigger UI update for delivery status change
-        DispatchQueue.main.async { [weak self] in
-            self?.objectWillChange.send()
-        }
-        
-    }
-    
-    // MARK: - Helper for System Messages
-    private func addSystemMessage(_ content: String, timestamp: Date = Date()) {
-        let systemMessage = BitchatMessage(
-            sender: "system",
-            content: content,
-            timestamp: timestamp,
-            isRelay: false
         )
+    }
+
+    // MARK: - Helper for System Messages (Using SystemMessagingService)
+    private func addSystemMessage(_ content: String, timestamp: Date = Date()) {
+        let systemMessage = systemMessaging.createSystemMessage(content: content, timestamp: timestamp)
         messages.append(systemMessage)
     }
 
@@ -4158,12 +4131,7 @@ final class ChatViewModel: ObservableObject, BitchatDelegate {
     /// If mesh is currently active, also append to the visible `messages`.
     @MainActor
     private func addMeshOnlySystemMessage(_ content: String) {
-        let systemMessage = BitchatMessage(
+        let systemMessage = systemMessaging.createSystemMessage(content: content)
-            sender: "system",
-            content: content,
-            timestamp: Date(),
-            isRelay: false
-        )
         // Persist to mesh timeline
         meshTimeline.append(systemMessage)
         trimMeshTimelineIfNeeded()
@@ -4178,12 +4146,7 @@ final class ChatViewModel: ObservableObject, BitchatDelegate {
     /// Also persists the message into the active channel's backing store so it survives timeline rebinds.
     @MainActor
     func addPublicSystemMessage(_ content: String) {
-        let systemMessage = BitchatMessage(
+        let systemMessage = systemMessaging.createSystemMessage(content: content)
-            sender: "system",
-            content: content,
-            timestamp: Date(),
-            isRelay: false
-        )
         // Append to current visible messages
         messages.append(systemMessage)
         // Persist into the backing store for the active channel to survive rebinds