Platforms Impacted

• iOS
• visionOS
• macOS

Description of changes

Regression introduced by #2198 . Since Mac Catalyst can import UIKit and AppKit, we end up duplicate definitions for various extensions. Fix is relatively simple, for the platform extensions we now only include the AppKit version when not building for Mac Catalyst.

Binary change

N/A, should have no impact on iOS binary size.

Verification

Swift package for FluentUI was built for iOS, visionOS, macOS, and macOS (Catalyst). I confirmed that the package builds properly for all supported platforms listed in the package definition.

Pull request checklist

This PR has considered:

• Light and Dark appearances
• iOS supported versions (all major versions greater than or equal current target deployment version)
• VoiceOver and Keyboard Accessibility
• Internationalization and Right to Left layouts
• Different resolutions (1x, 2x, 3x)
• Size classes and window sizes (iPhone vs iPad, notched devices, multitasking, different window sizes, etc)
• iPad Pointer interaction
• SwiftUI consumption (validation or new demo scenarios needed)
• Objective-C exposure (provide it only if needed)

Microsoft Reviewers: Open in CodeFlow