Refactor picker window handling and csproj conditions

Refactored window retrieval in file/folder pickers to use pattern matching for clarity and modern C# style. Updated picker instantiation to use AppWindow.Id directly. Removed unused using statements. Changed csproj Windows ItemGroup condition to use $(NetVersion) for better .NET version flexibility. Cleaned up cancellation token registration variable naming.

Author: VladislavAntonyuk

src/CommunityToolkit.Maui.Core/CommunityToolkit.Maui.Core.csproj

@@ -63,7 +63,7 @@
     <PackageReference Include="Tizen.UIExtensions.NUI" Version="*" />
   </ItemGroup>
 
-  <ItemGroup Condition="'$(TargetFramework)' == 'net10.0-windows10.0.19041.0'">
+  <ItemGroup Condition="'$(TargetFramework)' == '$(NetVersion)-windows10.0.19041.0'">
     <PackageReference Include="System.Speech" Version="10.0.1" />
     <PackageReference Include="Microsoft.WindowsAppSDK" Version="2.0.0-experimental3" />
   </ItemGroup>

src/CommunityToolkit.Maui.Core/Essentials/FileSaver/FileSaverImplementation.windows.cs

@@ -1,5 +1,3 @@
-using System;
-using System.Diagnostics;
 using Microsoft.Windows.Storage.Pickers;
 
 namespace CommunityToolkit.Maui.Storage;
@@ -11,13 +9,12 @@ public sealed partial class FileSaverImplementation : IFileSaver
 
 	async Task<string> InternalSaveAsync(string initialPath, string fileName, Stream stream, IProgress<double>? progress, CancellationToken cancellationToken)
 	{
-		var window = IPlatformApplication.Current?.Application.Windows[0].Handler?.PlatformView as MauiWinUIWindow;
-		if (window is null)
+		if (IPlatformApplication.Current?.Application.Windows[0].Handler?.PlatformView is not MauiWinUIWindow window)
 		{
 			throw new FileSaveException(
 				"Cannot present file picker: No active window found. Ensure the app is active with a visible window.");
 		}
-		
+
 		var savePicker = new FileSavePicker(window.AppWindow.Id)
 		{
 			SuggestedStartLocation = PickerLocationId.DocumentsLibrary,
@@ -34,7 +31,7 @@ async Task<string> InternalSaveAsync(string initialPath, string fileName, Stream
 		savePicker.FileTypeChoices.Add("All files", allFilesExtension);
 
 		var filePickerOperation = savePicker.PickSaveFileAsync();
-		await using var taskCompetedSource = cancellationToken.Register(CancelFilePickerOperation);
+		await using var _ = cancellationToken.Register(CancelFilePickerOperation);
 		var file = await filePickerOperation;
 		if (file is null)
 		{

src/CommunityToolkit.Maui.Core/Essentials/FolderPicker/FolderPickerImplementation.windows.cs

@@ -1,5 +1,3 @@
-using System;
-using System.Diagnostics;
 using CommunityToolkit.Maui.Core.Primitives;
 using Microsoft.Maui.ApplicationModel;
 using Microsoft.UI;
@@ -14,12 +12,12 @@ public sealed partial class FolderPickerImplementation : IFolderPicker
 	async Task<Folder> InternalPickAsync(string initialPath, CancellationToken cancellationToken)
 	{
 		cancellationToken.ThrowIfCancellationRequested();
-		var window = IPlatformApplication.Current?.Application.Windows[0].Handler?.PlatformView as MauiWinUIWindow;
-		if (window is null)
+		if (IPlatformApplication.Current?.Application.Windows[0].Handler?.PlatformView is not MauiWinUIWindow window)
 		{
 			throw new FolderPickerException(
 				"Cannot present folder picker: No active window found. Ensure the app is active with a visible window.");
 		}
+
 		var folderPicker = new Microsoft.Windows.Storage.Pickers.FolderPicker(window.AppWindow.Id)
 		{
 			SuggestedStartLocation = PickerLocationId.DocumentsLibrary,