Extend sync scrolling to `.. included::` files

[alcarney]

What would you like to see

Sync scrolling should also work in included files, off the top of my the following will need to be implemented

• [ ] Implement an include-read event handler in the sphinx-agent, (Sphinx v7+ only)
• [ ] Extend the line number transform to also include src uri/path
• [ ] Come up with some solution for scrolling the preview view between file contexts (related to #704)