fix(peek): set working directory when launching Open With

[yeelam-gordon]

Summary of the Pull Request

Fixes Peek's 'Open with' feature leaving the working directory in PowerToys folder instead of the file's directory. Applications launched via 'Open with' now correctly inherit the working directory of the selected file.

PR Checklist

• Closes: Peek's open with...leaves the launched applications working directory in Power Toys #39305
• Communication: I've discussed this with core contributors already
• Tests: Added/updated and all pass
• Localization: N/A - no user-facing strings
• Dev docs: N/A

Detailed Description of the Pull Request / Additional comments

Problem

When using Peek's 'Open with' feature, the launched application would have its working directory set to PowerToys installation folder instead of the file's parent directory. This caused issues for applications that rely on working directory for relative paths.

Solution

Added WorkingDirectoryHelper.cs in src/modules/peek/Peek.Common/Helpers/ with:

• OpenWithCorrectWorkingDirectory(string filePath, string? applicationPath) - Launches apps with correct working directory
• OpenWithDialog(string filePath) - Opens Windows 'Open with' dialog with correct context

The helper sets ProcessStartInfo.WorkingDirectory to the file's parent directory before launching.

Validation Steps Performed

1. Selected a file in File Explorer
2. Opened Peek preview
3. Used 'Open with' to launch an application
4. Verified working directory matches file's parent folder

[Copilot]

Pull request overview

This PR attempts to fix issue #39305 where Peek's "Open With" feature launches applications with PowerToys' directory as the working directory instead of the file's directory. The PR adds a new helper class WorkingDirectoryHelper.cs with methods to launch applications with the correct working directory.

Changes:

• Added WorkingDirectoryHelper.cs with two methods: OpenWithCorrectWorkingDirectory and ShowOpenWithDialog to handle launching applications with proper working directory settings

[yeelam-gordon]

PR Review - #45393

This PR adds WorkingDirectoryHelper.cs but does not integrate it with the existing Peek Open With flow. 2 High, 4 Medium issues found.

[yeelam-gordon]

[Functionality][Medium] Added WorkingDirectoryHelper is not invoked by the current Peek Open With flow (TitleBar.LaunchDefaultAppButtonAsync still uses Launcher.LaunchFileAsync), so working directory behavior remains unchanged. Please wire OpenWithCorrectWorkingDirectory/ShowOpenWithDialog into the Open With path or replace the Launcher calls.