fix(appstate): replace isolated deinit with nonisolated(unsafe) cleanup

The production release compiler rejects `isolated deinit` (SE-0371) as an
experimental feature and won't let it be enabled, so `swift build -c release`
(the DMG build) failed. Use a plain deinit and mark the torn-down stored
properties nonisolated(unsafe) — runtime behavior is unchanged and no
experimental feature is required.

Author: lltx

Sources/CodeIsland/AppState.swift

@@ -112,19 +112,19 @@ final class AppState {
     }
 
     private var maxHistory: Int { SettingsManager.shared.maxToolHistory }
-    private var cleanupTimer: Timer?
+    nonisolated(unsafe) private var cleanupTimer: Timer?
     private var autoCollapseTask: Task<Void, Never>?
     private var completionQueue: [String] = []
     /// Mouse must enter the panel before auto-collapse is allowed (prevents instant dismiss)
     var completionHasBeenEntered = false
     /// Auto-collapse timer fired but mouse is inside panel — defer collapse until mouse leaves
     var deferCollapseOnMouseLeave = false
-    private var processMonitors: [String: (source: DispatchSourceProcess, process: ProcessIdentity)] = [:]
+    nonisolated(unsafe) private var processMonitors: [String: (source: DispatchSourceProcess, process: ProcessIdentity)] = [:]
     private var exitingSessions: [String: ProcessIdentity] = [:]
-    private var saveTimer: Timer?
-    private var fsEventStream: FSEventStreamRef?
+    nonisolated(unsafe) private var saveTimer: Timer?
+    nonisolated(unsafe) private var fsEventStream: FSEventStreamRef?
     private var lastFSScanTime: Date = .distantPast
-    private var discoveryScanTask: Task<Void, Never>?
+    nonisolated(unsafe) private var discoveryScanTask: Task<Void, Never>?
     private var pendingDiscoveryRescan = false
     private var isShowingCompletion: Bool {
         if case .completionCard = surface { return true }
@@ -152,7 +152,7 @@ final class AppState {
         guard let rid = rotatingSessionId else { return nil }
         return sessions[rid]
     }
-    private var rotationTimer: Timer?
+    nonisolated(unsafe) private var rotationTimer: Timer?
 
     private func startCleanupTimer() {
         guard cleanupTimer == nil else { return }
@@ -2523,7 +2523,11 @@ final class AppState {
         for key in Array(processMonitors.keys) { stopMonitor(key) }
     }
 
-    isolated deinit {
+    // Plain (nonisolated) deinit: the accessed stored properties are marked
+    // `nonisolated(unsafe)` so they can be torn down here. `isolated deinit`
+    // (SE-0371) is rejected by the production release compiler, so it can't be
+    // used. At dealloc there are no other references, so these accesses don't race.
+    deinit {
         rotationTimer?.invalidate()
         cleanupTimer?.invalidate()
         saveTimer?.invalidate()