Swift 6 strict concurrency support

[sbooth]

The thread-safety of the various AudioObject APIs isn't clear. Lacking documentation to the contrary I assume they aren't thread-safe, which means that the current design for AudioSystemObject needs to be revisited.

[Copilot]

Pull Request Overview

Adds strict concurrency support by marking AudioObject and its subclasses as @unchecked Sendable, and updates the property change notification block to be @Sendable.

• Introduces @unchecked Sendable conformance to AudioObject base class and all subclasses
• Updates PropertyChangeNotificationBlock alias to @Sendable
• Bumps copyright year in AudioEndpoint.swift

Reviewed Changes

Copilot reviewed 21 out of 21 changed files in this pull request and generated no comments.

File	Description
AudioObject.swift	Added @unchecked Sendable to AudioObject and made its notification block @Sendable
AudioControl.swift and other subclasses	Added redundant @unchecked Sendable conformance to each subclass of AudioObject
AudioEndpoint.swift	Updated copyright years

Comments suppressed due to low confidence (3)

Sources/CAAudioHardware/AudioObject.swift:12

• [nitpick] Add a brief doc comment explaining why AudioObject is marked @unchecked Sendable (e.g., underlying C API assumptions) to clarify the concurrency guarantee for future maintainers.

public class AudioObject: Equatable, Hashable, @unchecked Sendable, CustomDebugStringConvertible {

Sources/CAAudioHardware/AudioObject.swift:85

• Consider adding unit or integration tests that exercise PropertyChangeNotificationBlock under concurrent usage to verify the notification closure behaves correctly across threads.

	public typealias PropertyChangeNotificationBlock = @Sendable (_ changes: [PropertyAddress]) -> Void

Sources/CAAudioHardware/AudioControl.swift:15

• [nitpick] Since AudioControl inherits from AudioObject which is already declared @unchecked Sendable, you can remove the redundant @unchecked Sendable conformance here to reduce duplication.

public class AudioControl: AudioObject, @unchecked Sendable {