[Feature Request] Diff review pane: add file collapse/expand, context expansion, and prompt line removal

Bug Description
The diff review pane could use some features. this is in the tui fullscreen mode

1. i can't interact with the files when it's open; i'd like to be able to collapse / expand different file diffs
2. when a new file is created, even after adding with git add it won't show the diff and says "New file not yet staged. Run git add ... to see line counts". i close the pane and reopen it to get it to refresh.
3. i'd like the ability to expand other lines in the review that aren't changes. for instance, maybe i'd like to click and expand the lines above a displayed diff
4. when i highlight lines in the diff and it injects them in my prompt, i can't then remove them from my prompt

Environment Info

• Platform: linux
• Terminal: xterm-256color
• Version: 2.1.270
• Feedback ID: 3f0d1fb5-504d-4187-98c5-c2f0a64f710f

Errors

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