Platforms Impacted

• iOS
• visionOS
• macOS

Description of changes

Glassify BottomCommandingController. We already glassified it when it was a sheet, update it for when it's a bottom bar as well. On iOS 26, use UIGlassEffect. On lower OSs, use UIBlurEffect for a fake glass look.

• New BottomCommandingControllerStyle that's just an alias
• Apply background color to UIGlassEffect only
  • No way to tint UIBlurEffect
• Use new UICornerConfiguration on iOS 26
  • Manually update CALayer on lower OSs

Verification

Visual Verification

Primary	UIBlurEffect	UIGlassEffect

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