Fixes #32257 /claim #32257

Implemented commenting on unchanged lines in Pull Request diffs, lines are accessed by expanding the diff preview. Comments also appear in the “Files Changed” tab on the unchanged lines where they were placed.

Screenshots

• Comment form on expanded lines not in diff

• Comments available to view on Files Changed tab, with badge indicating that there are hidden comments available to view.

https://github.com/user-attachments/assets/f7919386-9824-4ab0-9b19-4051b1473673

• Comments available to view on Conversation tab, with line context preview to show where they are located.

• Full commenting process

https://github.com/user-attachments/assets/5d088a1f-9ab1-445e-8a68-60db63c7907c

• Shared link expands to hidden comment

https://github.com/user-attachments/assets/c0dc8c5d-0ae9-41a0-9697-cdbcc1a2909e