Fix Windows Picker Initial Path is not set

[VladislavAntonyuk]

Description of Change

Set initial folder for FilePicker and FolderPicker on Windows

PR Checklist

• Has a linked Issue, and the Issue has been approved(bug) or Championed (feature/proposal)
• Has tests (if omitted, state reason in description)
• Has samples (if omitted, state reason in description)
• Rebased on top of main at time of PR
• Changes adhere to coding standard
• Documentation created or updated: https://github.com/MicrosoftDocs/CommunityToolkit/pulls

Additional information

[Copilot]

Pull request overview

This PR fixes the initial path/folder functionality for Windows file and folder pickers by migrating from the older Windows.Storage.Pickers API to the newer Microsoft.Windows.Storage.Pickers API. The implementation now properly sets the suggested folder path when opening pickers.

Key changes:

• Migrated to Microsoft.Windows.Storage.Pickers API for both FolderPicker and FileSaver on Windows
• Implemented proper window retrieval using IPlatformApplication and MauiWinUIWindow
• Added SuggestedFolder property to set initial path for pickers
• Enhanced error handling by separating cancellation from folder existence errors

Reviewed changes

Copilot reviewed 5 out of 5 changed files in this pull request and generated 8 comments.

Show a summary per file

File	Description
FolderPickerImplementation.windows.cs	Updated to use new Windows picker API with proper initial path support and window handling
FileSaverImplementation.windows.cs	Updated to use new Windows picker API with proper initial path support and window handling
CommunityToolkit.Maui.Core.csproj	Added Microsoft.WindowsAppSDK dependency and updated System.Speech version
FolderPickerViewModel.cs	Sample code updated to demonstrate initial folder path usage
FileSaverViewModel.cs	Sample code updated to demonstrate initial folder path usage

[Copilot]

Pull request overview

Copilot reviewed 5 out of 5 changed files in this pull request and generated 3 comments.