fix(vscode): reopen files that were open before diff view

[zhanba]

Screen record

• https://jam.dev/c/94fe69ba-51b1-4bea-a02a-78b13954c65f

Summary

• Fixes issue where files open in VSCode before creating a diff view would remain closed after accepting or rejecting changes
• Tracks whether a file was open before the diff view via wasFileOpenBeforeDiff property
• Automatically reopens the file after applying changes if it was previously open
• Adds isFileCurrentlyOpen utility to detect open files (excluding diff views)

This improves the user experience by preserving their workspace state when working with diff views.

Changes

• Added wasFileOpenBeforeDiff property to DiffView class to track file state
• Modified DiffView constructor to accept and store the open file state
• Enhanced acceptChanges method to conditionally reopen files
• Added isFileCurrentlyOpen utility function to check if file is open in tabs
• Updated DiffView.create to detect and pass the current file state

Test plan

• Verify that files open before diff view are reopened after accepting changes
• Verify that files not previously open remain closed after diff operations
• Test with various file types and edge cases
• Ensure no regression in existing diff view functionality

🤖 Generated with Pochi

[wsxiaoys]

a few nits, otherwise LGTM