[ClassKit] Update bindings to Xcode 26.4 Release Candidate (#24946)

Author: dalexsoto

src/classkit.cs

@@ -546,8 +546,27 @@ interface CLSDataStore {
 		[Async]
 		[Export ("fetchActivityForURL:completion:")]
 		void FetchActivity (NSUrl url, Action<CLSActivity, NSError> completion);
+
+		[MacCatalyst (26, 4)]
+		[Mac (26, 4)]
+		[iOS (26, 4)]
+		[Async (XmlDocs = """
+			<param name="documentUrl">The URL of the document to check.</param>
+			<summary>Asynchronously checks whether the specified document is assigned and returns a task that contains the result.</summary>
+			<returns>A task that contains the result of the check.</returns>
+			<remarks>To be added.</remarks>
+			""")]
+		[Export ("checkIsAssignedDocument:completion:")]
+		void CheckIsAssignedDocument (NSUrl documentUrl, CLSDataStoreCheckAssignedDocumentCompletionHandler completion);
 	}
 
+	/// <summary>Completion handler for <see cref="CLSDataStore.CheckIsAssignedDocument" />.</summary>
+	[MacCatalyst (26, 4)]
+	[Mac (26, 4)]
+	[iOS (26, 4)]
+	[NoTV]
+	delegate void CLSDataStoreCheckAssignedDocumentCompletionHandler (bool isAssigned, [NullAllowed] NSError error);
+
 	/// <summary>Represents a quantitative data item.</summary>
 	[Introduced (PlatformName.MacCatalyst, 14, 0)]
 	[NoTV]