fix(skills): improve code examples in iOS 26 skills

- Add do-catch error handling to SwiftUI streaming example in
  foundation-models-on-device
- Add Auto Layout constraints to UIKit glass effect example in
  liquid-glass-design
- Promote build settings prerequisite from code comment to visible
  blockquote warning in swift-concurrency-6-2

skills/foundation-models-on-device/SKILL.md

@@ -178,6 +178,7 @@ for try await partial in stream {
 
 ```swift
 @State private var partialResult: TripIdeas.PartiallyGenerated?
+@State private var errorMessage: String?
 
 var body: some View {
     List {
@@ -185,11 +186,18 @@ var body: some View {
             Text(idea)
         }
     }
+    .overlay {
+        if let errorMessage { Text(errorMessage).foregroundStyle(.red) }
+    }
     .task {
+        do {
             let stream = session.streamResponse(to: prompt, generating: TripIdeas.self)
             for try await partial in stream {
                 partialResult = partial
             }
+        } catch {
+            errorMessage = error.localizedDescription
+        }
     }
 }
 ```

skills/liquid-glass-design/SKILL.md

@@ -138,13 +138,27 @@ glassEffect.tintColor = UIColor.systemBlue.withAlphaComponent(0.3)
 glassEffect.isInteractive = true
 
 let visualEffectView = UIVisualEffectView(effect: glassEffect)
+visualEffectView.translatesAutoresizingMaskIntoConstraints = false
 visualEffectView.layer.cornerRadius = 20
 visualEffectView.clipsToBounds = true
 
+view.addSubview(visualEffectView)
+NSLayoutConstraint.activate([
+    visualEffectView.centerXAnchor.constraint(equalTo: view.centerXAnchor),
+    visualEffectView.centerYAnchor.constraint(equalTo: view.centerYAnchor),
+    visualEffectView.widthAnchor.constraint(equalToConstant: 200),
+    visualEffectView.heightAnchor.constraint(equalToConstant: 120)
+])
+
 // Add content to contentView
 let label = UILabel()
 label.text = "Liquid Glass"
+label.translatesAutoresizingMaskIntoConstraints = false
 visualEffectView.contentView.addSubview(label)
+NSLayoutConstraint.activate([
+    label.centerXAnchor.constraint(equalTo: visualEffectView.contentView.centerXAnchor),
+    label.centerYAnchor.constraint(equalTo: visualEffectView.contentView.centerYAnchor)
+])
 ```
 
 ### UIGlassContainerEffect for Multiple Elements

skills/swift-concurrency-6-2/SKILL.md

@@ -136,10 +136,9 @@ This mode is opt-in and recommended for apps, scripts, and other executable targ
 
 When you need actual parallelism, explicitly offload with `@concurrent`:
 
+> **Important:** This example requires Approachable Concurrency build settings — SE-0466 (MainActor default isolation) and SE-0461 (NonisolatedNonsendingByDefault). With these enabled, `extractSticker` stays on the caller's actor, making mutable state access safe. **Without these settings, this code has a data race** — the compiler will flag it.
+
 ```swift
-// Assumes Approachable Concurrency build settings are enabled:
-// SE-0466 (MainActor default isolation) and SE-0461 (NonisolatedNonsendingByDefault).
-// Safe mutation of cachedStickers via await depends on these compiler options.
 nonisolated final class PhotoProcessor {
     private var cachedStickers: [String: Sticker] = [:]