Keep capture work off the main thread

Move the expensive accessibility snapshot crawl off MainActor while keeping the frontmost-app lookup on the UI thread to reduce brief beachballs when reopening the app.

Author: ComputelessComputer

Sources/OpenbirdKit/Capture/AccessibilitySnapshotter.swift

@@ -29,7 +29,6 @@ public struct AccessibilitySnapshotter: Sendable {
 
     public init() {}
 
-    @MainActor
     func snapshotFrontmostWindow(for application: FrontmostApplicationContext) -> WindowSnapshot? {
         if shouldUseMinimalSnapshot(for: application) {
             let snapshot = snapshotSanitizer.sanitize(minimalSnapshot(for: application))

Sources/OpenbirdKit/Capture/CollectorRuntime.swift

@@ -169,9 +169,7 @@ public final class CollectorRuntime: NSObject, @unchecked Sendable {
                 return
             }
 
-            guard var snapshot = await MainActor.run(body: {
-                snapshotter.snapshotFrontmostWindow(for: frontmostApplication)
-            }) else {
+            guard var snapshot = snapshotter.snapshotFrontmostWindow(for: frontmostApplication) else {
                 _ = try await persistCollectorStatus("idle", heartbeat: now)
                 return
             }