Fix nested path resolution failure

[CalvinAllen]

Summary

• Fixes Couldn't Resolve Folder in Nested Path #5
• Removes WorkingDirectory from ProcessStartInfo as it was incorrectly being set to a file path instead of a directory path
• This caused failures when opening files in deeply nested paths

Root Cause

ProcessStartInfo.WorkingDirectory expects a directory path, but selectedFilePath is a file path (e.g., C:\...\file.h). For deeply nested or long paths, this would cause the process to fail, resulting in "Couldn't resolve the folder" error.

Test plan

• Open a solution with deeply nested files (5+ levels deep)
• Right-click on a file in a nested path and select "Open in Notepad++"
• Verify the file opens correctly in Notepad++