Fix six Swift 6 strict-concurrency errors

- PresentationManager: screen-change observer asserts MainActor (queue: .main)
- BibleView / MainControlView: dropped-URL collection behind OSAllocatedUnfairLock
  instead of mutating a captured var across provider callback threads
- PreviewPanelView: ForceTouch view teardown via isolated deinit (SE-0371)
- WindowNotifications: PresentationCommandRouter handlers typed @mainactor
- TextBoxLayout: transitionRow get/set typed @mainactor; pass { get() } to
  Binding — the direct function value makes swift-frontend crash emitting an
  @isolated(any) reabstraction thunk (Xcode 26.2 IRGen SmallVector abort)

Author: RobyRew

TopPresenter/Core/PresentationManager.swift

@@ -927,7 +927,11 @@ final class PresentationManager {
             object: nil,
             queue: .main
         ) { [weak self] _ in
-            self?.handleScreenConfigurationChange()
+            // queue: .main guarantees main-thread delivery; the closure is just
+            // typed nonisolated @Sendable, so assert the isolation for Swift 6.
+            MainActor.assumeIsolated {
+                self?.handleScreenConfigurationChange()
+            }
         }
     }
 

TopPresenter/Views/Bible/BibleView.swift

@@ -8,6 +8,7 @@
 import SwiftUI
 import SwiftData
 import UniformTypeIdentifiers
+import os
 
 /// Main Bible view with module selection, book/chapter navigation, search, and verse display.
 struct BibleView: View {
@@ -1388,16 +1389,16 @@ struct BibleImportSheet: View {
     /// Load dropped file URLs asynchronously, then route them.
     private func loadDroppedURLs(_ providers: [NSItemProvider]) {
         let group = DispatchGroup()
-        let lock = NSLock()
-        var urls: [URL] = []
+        // Provider callbacks arrive on arbitrary threads — collect behind a lock.
+        let collected = OSAllocatedUnfairLock(initialState: [URL]())
         for p in providers where p.canLoadObject(ofClass: URL.self) {
             group.enter()
             _ = p.loadObject(ofClass: URL.self) { url, _ in
-                if let url { lock.lock(); urls.append(url); lock.unlock() }
+                if let url { collected.withLock { $0.append(url) } }
                 group.leave()
             }
         }
-        group.notify(queue: .main) { handleSelectedURLs(urls) }
+        group.notify(queue: .main) { handleSelectedURLs(collected.withLock { $0 }) }
     }
 
     /// One file → inline single-import flow (detect/override format). Multiple

TopPresenter/Views/Main/MainControlView.swift

@@ -8,6 +8,7 @@
 import SwiftUI
 import SwiftData
 import UniformTypeIdentifiers
+import os
 
 /// The main control window - split into sidebar, content area, and preview panel.
 struct MainControlView: View {
@@ -265,9 +266,8 @@ struct MainControlView: View {
     }
 
     private func handleDrop(providers: [NSItemProvider]) {
-        // Provider callbacks arrive on arbitrary threads — serialize the appends.
-        let lock = NSLock()
-        var urls: [URL] = []
+        // Provider callbacks arrive on arbitrary threads — collect behind a lock.
+        let collected = OSAllocatedUnfairLock(initialState: [URL]())
         let group = DispatchGroup()
 
         for provider in providers {
@@ -277,14 +277,13 @@ struct MainControlView: View {
                 if let data = data as? Data,
                    let urlString = String(data: data, encoding: .utf8),
                    let url = URL(string: urlString) {
-                    lock.lock()
-                    urls.append(url)
-                    lock.unlock()
+                    collected.withLock { $0.append(url) }
                 }
             }
         }
 
         group.notify(queue: .main) { [self] in
+            let urls = collected.withLock { $0 }
             guard !urls.isEmpty else { return }
             Task {
                 // EXPAND folders first (max 2 subfolder levels, USFM kept whole) —

TopPresenter/Views/Main/PreviewPanelView.swift

@@ -1262,7 +1262,9 @@ struct ForceTouchDetector: NSViewRepresentable {
             return nil
         }
 
-        deinit {
+        // isolated deinit (SE-0371): runs on the main actor — NSEvent monitor
+        // teardown touches NSView-isolated state.
+        isolated deinit {
             removeMonitor()
         }
     }

TopPresenter/Views/Main/WindowNotifications.swift

@@ -97,9 +97,11 @@ final class PresentationCommandRouter {
 
     init(pm: PresentationManager) {
         let center = NotificationCenter.default
-        func on(_ name: Notification.Name, _ handler: @escaping () -> Void) {
+        func on(_ name: Notification.Name, _ handler: @escaping @MainActor () -> Void) {
             tokens.append(center.addObserver(forName: name, object: nil, queue: .main) { _ in
-                handler()
+                // queue: .main guarantees main-thread delivery; the observer
+                // closure is typed nonisolated @Sendable, so assert isolation.
+                MainActor.assumeIsolated(handler)
             })
         }
 

TopPresenter/Views/Presentation/TextBoxLayout.swift

@@ -3600,11 +3600,14 @@ struct LayoutEditorSheet: View {
     @ViewBuilder
     private func transitionRow(
         label: String, help: String,
-        get: @escaping () -> String, set: @escaping (String) -> Void
+        get: @escaping @MainActor () -> String, set: @escaping @MainActor (String) -> Void
     ) -> some View {
         labeledRow(label) {
+            // `{ get() }` not `get` — passing the function value directly makes the
+            // compiler emit an @isolated(any) reabstraction thunk that crashes
+            // swift-frontend (Xcode 26.2 IRGen, SmallVector capacity abort).
             Picker("", selection: Binding(
-                get: get,
+                get: { get() },
                 set: { raw in
                     set(raw)
                     playTransitionPreview(raw)