Address review: named constant for accessibilityLabel suppression

Add AttributedLabel/Label.suppressedAccessibilityLabel so the "" suppression
value is greppable and legible at the call site (per Rob's review), and rename
the suppression test to flag that it guards an undocumented UIKit behavior.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

Author: RoyalPineapple

BlueprintUICommonControls/Sources/AttributedLabel.swift

@@ -80,12 +80,15 @@ public struct AttributedLabel: Element, Hashable {
     /// Overrides the automatically-derived accessibility label.
     ///
     /// When `nil` (the default), the label is derived from the displayed text — current behavior.
-    /// Provide a string to override it, or `""` to suppress the spoken label entirely. Suppression
-    /// is useful when the text is surfaced through `accessibilityValue` / `accessibilityHint`
-    /// instead, so the content is not announced twice (e.g. when this label is merged into a
-    /// combined accessibility element).
+    /// Provide a string to override it, or `suppressedAccessibilityLabel` (`""`) to suppress the
+    /// spoken label entirely. Suppression is useful when the text is surfaced through
+    /// `accessibilityValue` / `accessibilityHint` instead, so the content is not announced twice
+    /// (e.g. when this label is merged into a combined accessibility element).
     public var accessibilityLabel: String?
 
+    /// Assign to `accessibilityLabel` to suppress the spoken label entirely (see that property).
+    public static let suppressedAccessibilityLabel = ""
+
     /// A localized string that represents the current value of the accessibility element.
     ///
     /// The value is a localized string that contains the current value of an element.

BlueprintUICommonControls/Sources/Label.swift

@@ -60,12 +60,15 @@ public struct Label: ProxyElement {
     /// Overrides the automatically-derived accessibility label.
     ///
     /// When `nil` (the default), the label is derived from the displayed text — current behavior.
-    /// Provide a string to override it, or `""` to suppress the spoken label entirely. Suppression
-    /// is useful when the text is surfaced through `accessibilityValue` / `accessibilityHint`
-    /// instead, so the content is not announced twice (e.g. when this label is merged into a
-    /// combined accessibility element).
+    /// Provide a string to override it, or `suppressedAccessibilityLabel` (`""`) to suppress the
+    /// spoken label entirely. Suppression is useful when the text is surfaced through
+    /// `accessibilityValue` / `accessibilityHint` instead, so the content is not announced twice
+    /// (e.g. when this label is merged into a combined accessibility element).
     public var accessibilityLabel: String?
 
+    /// Assign to `accessibilityLabel` to suppress the spoken label entirely (see that property).
+    public static let suppressedAccessibilityLabel = ""
+
     /// A localized string that represents the current value of the accessibility element.
     ///
     /// The value is a localized string that contains the current value of an element.

BlueprintUICommonControls/Tests/Sources/AttributedLabelTests.swift

@@ -115,12 +115,14 @@ class AttributedLabelTests: XCTestCase {
         XCTAssertEqual(labelView.accessibilityLabel, "Custom")
     }
 
-    func test_accessibilityLabel_suppressed() {
+    // Load-bearing: guards the undocumented UIKit behavior that `""`-suppression relies on.
+    func test_accessibilityLabel_suppressed_guardsUIKitEmptyStringBehavior() {
         // An empty string suppresses the spoken label entirely: the backing view reports "",
         // *not* the displayed text. (UILabel returns an explicitly-set empty string verbatim,
-        // rather than falling back to its text the way it does for `nil`.)
+        // rather than falling back to its text the way it does for `nil`.) If a future OS changed
+        // this fallback, `""`-suppression would silently break — hence this test.
         let label = AttributedLabel(attributedText: NSAttributedString(string: "Hello, World!")) {
-            $0.accessibilityLabel = ""
+            $0.accessibilityLabel = AttributedLabel.suppressedAccessibilityLabel
         }
 
         let labelView = AttributedLabel.LabelView()
@@ -143,7 +145,7 @@ class AttributedLabelTests: XCTestCase {
         labelView.update(model: label, text: label.displayableAttributedText, environment: .empty, isMeasuring: false)
         XCTAssertEqual(labelView.accessibilityLabel, "Custom")
 
-        label.accessibilityLabel = ""
+        label.accessibilityLabel = AttributedLabel.suppressedAccessibilityLabel
         labelView.update(model: label, text: label.displayableAttributedText, environment: .empty, isMeasuring: false)
         XCTAssertEqual(labelView.accessibilityLabel, "")
 
@@ -158,7 +160,7 @@ class AttributedLabelTests: XCTestCase {
         // merged into a composite accessibility element — the empty label is filtered out, so the
         // content isn't announced twice.
         let label = AttributedLabel(attributedText: NSAttributedString(string: "Displayed text")) {
-            $0.accessibilityLabel = ""
+            $0.accessibilityLabel = AttributedLabel.suppressedAccessibilityLabel
             $0.accessibilityValue = "X"
         }