## Why
Long drafts need to remain browsable while leaving room for the transcript. Remote image attachments also need to leave an editable prompt row visible.
## What changed
- Cap the fullscreen composer, including padding and hints, at two-thirds of the screen, with a minimum of eight rows when the screen allows.
- Support mouse-wheel browsing without moving the caret or changing transcript selection, search, or activity focus. Show arrows for hidden prompt rows and hide the cursor when the caret is offscreen.
- Resume caret following on editor input, paste, and external edits.
- Keep the selected remote image visible while reserving space for prompt text.
## Testing
Add regression tests and snapshots for fullscreen scrolling, caret restoration after navigation, paste and external edits, remote image navigation and deletion, resizing at scroll boundaries, and disconnected editing.
GitOrigin-RevId: 9a1e4ce14b3b3747e6d136207546327531339258
Ian MacLeod
6ece7bfc21