Fix Swift 6 actor-isolation warnings in model inits and services

- Message, Conversation, EmailLog: add nonisolated to inits — plain value
  types have no actor isolation, but the macOS 27 SDK was inferring it
- EncryptionService: replace lazy var encryptionKey (which mutates self and
  gets inferred as @MainActor) with an eagerly-initialized let in init()
- FileLogger: add nonisolated to shared, write, and minimumLevel so they
  are callable from nonisolated AppLogger methods without warnings
- LogLevel.<: add nonisolated to the Comparable conformance method

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

oAI/Models/Conversation.swift

@@ -33,7 +33,7 @@ struct Conversation: Identifiable, Codable {
     var updatedAt: Date
     var primaryModel: String? // Primary model used in this conversation
 
-    init(
+    nonisolated init(
         id: UUID = UUID(),
         name: String,
         messages: [Message] = [],

oAI/Models/EmailLog.swift

@@ -44,7 +44,7 @@ struct EmailLog: Identifiable, Codable, Equatable {
     let responseTime: TimeInterval? // Time to generate response in seconds
     let modelId: String? // Model that handled the email
 
-    init(
+    nonisolated init(
         id: UUID = UUID(),
         timestamp: Date = Date(),
         sender: String,

oAI/Models/Message.swift

@@ -66,7 +66,7 @@ struct Message: Identifiable, Codable, Equatable {
     // Reasoning/thinking content (not persisted — in-memory only)
     var thinkingContent: String? = nil
 
-    init(
+    nonisolated init(
         id: UUID = UUID(),
         role: MessageRole,
         content: String,

oAI/Services/EncryptionService.swift

@@ -31,12 +31,11 @@ import IOKit
 class EncryptionService {
     nonisolated static let shared = EncryptionService()
 
-    private let salt = "oAI-secure-storage-v1" // App-specific salt
+    private let encryptionKey: SymmetricKey
-    private lazy var encryptionKey: SymmetricKey = {
-        deriveEncryptionKey()
-    }()
 
-    private init() {}
+    private init() {
+        self.encryptionKey = Self.deriveEncryptionKey()
+    }
 
     // MARK: - Public Interface
 
@@ -73,19 +72,17 @@ class EncryptionService {
     // MARK: - Key Derivation
 
     /// Derive encryption key from machine-specific data
-    private func deriveEncryptionKey() -> SymmetricKey {
+    private static func deriveEncryptionKey() -> SymmetricKey {
-        // Combine machine UUID + bundle ID + salt for key material
         let machineUUID = getMachineUUID()
         let bundleID = Bundle.main.bundleIdentifier ?? "com.oai.oAI"
+        let salt = "oAI-secure-storage-v1"
         let keyMaterial = "\(machineUUID)-\(bundleID)-\(salt)"
-
-        // Hash to create consistent 256-bit key
         let hash = SHA256.hash(data: Data(keyMaterial.utf8))
         return SymmetricKey(data: hash)
     }
 
     /// Get machine-specific UUID (IOPlatformUUID)
-    private func getMachineUUID() -> String {
+    private static func getMachineUUID() -> String {
         // Get IOPlatformUUID from IOKit
         let platformExpert = IOServiceGetMatchingService(
             kIOMainPortDefault,

oAI/Utilities/Logging.swift

@@ -52,7 +52,7 @@ enum LogLevel: Int, Comparable, CaseIterable, Sendable {
         }
     }
 
-    static func < (lhs: LogLevel, rhs: LogLevel) -> Bool {
+    nonisolated static func < (lhs: LogLevel, rhs: LogLevel) -> Bool {
         lhs.rawValue < rhs.rawValue
     }
 }
@@ -60,7 +60,7 @@ enum LogLevel: Int, Comparable, CaseIterable, Sendable {
 // MARK: - File Logger
 
 final class FileLogger: @unchecked Sendable {
-    static let shared = FileLogger()
+    nonisolated static let shared = FileLogger()
 
     private let fileHandle: FileHandle?
     private let queue = DispatchQueue(label: "com.oai.filelogger")
@@ -70,8 +70,8 @@ final class FileLogger: @unchecked Sendable {
         return f
     }()
 
-    /// Current minimum log level (read from UserDefaults for thread safety)
+    /// Current minimum log level (backed by UserDefaults — thread-safe).
-    var minimumLevel: LogLevel {
+    nonisolated var minimumLevel: LogLevel {
         get {
             let raw = UserDefaults.standard.integer(forKey: "logLevel")
             return LogLevel(rawValue: raw) ?? .info
@@ -95,7 +95,7 @@ final class FileLogger: @unchecked Sendable {
         fileHandle?.seekToEndOfFile()
     }
 
-    func write(_ level: LogLevel, category: String, message: String) {
+    nonisolated func write(_ level: LogLevel, category: String, message: String) {
         guard level >= minimumLevel else { return }
         queue.async { [weak self] in
             guard let self, let fh = self.fileHandle else { return }