## Summary
This PR makes app-server-provided image URLs first-class attachments in
TUI, so they survive resume/backtrack/history recall and are resubmitted
correctly.
<img width="715" height="491" alt="Screenshot 2026-02-12 at 8 27 08 PM"
src="https://github.com/user-attachments/assets/226cbd35-8f0c-4e51-a13e-459ef5dd1927"
/>
Can delete the attached image upon backtracking:
<img width="716" height="301" alt="Screenshot 2026-02-12 at 8 27 31 PM"
src="https://github.com/user-attachments/assets/4558d230-f1bd-4eed-a093-8e1ab9c6db27"
/>
In both history and composer, remote images are rendered as normal
`[Image #N]` placeholders, with numbering unified with local images.
## What changed
- Plumb remote image URLs through TUI message state:
- `UserHistoryCell`
- `BacktrackSelection`
- `ChatComposerHistory::HistoryEntry`
- `ChatWidget::UserMessage`
- Show remote images as placeholder rows inside the composer box (above
textarea), and in history cells.
- Support keyboard selection/deletion for remote image rows in composer
(`Up`/`Down`, `Delete`/`Backspace`).
- Preserve remote-image-only turns in local composer history (Up/Down
recall), including restore after backtrack.
- Ensure submit/queue/backtrack resubmit include remote images in model
input (`UserInput::Image`), and keep request shape stable for
remote-image-only turns.
- Keep image numbering contiguous across remote + local images:
- remote images occupy `[Image #1]..[Image #M]`
- local images start at `[Image #M+1]`
- deletion renumbers consistently.
- In protocol conversion, increment shared image index for remote images
too, so mixed remote/local image tags stay in a single sequence.
- Simplify restore logic to trust in-memory attachment order (no
placeholder-number parsing path).
- Backtrack/replay rollback handling now queues trims through
`AppEvent::ApplyThreadRollback` and syncs transcript overlay/deferred
lines after trims, so overlay/transcript state stays consistent.
- Trim trailing blank rendered lines from user history rendering to
avoid oversized blank padding.
## Docs + tests
- Updated: `docs/tui-chat-composer.md` (remote image flow,
selection/deletion, numbering offsets)
- Added/updated tests across `tui/src/chatwidget/tests.rs`,
`tui/src/app.rs`, `tui/src/app_backtrack.rs`, `tui/src/history_cell.rs`,
and `tui/src/bottom_pane/chat_composer.rs`
- Added snapshot coverage for remote image composer states, including
deleting the first of two remote images.
## Validation
- `just fmt`
- `cargo test -p codex-tui`
## Codex author
`codex fork 019c2636-1571-74a1-8471-15a3b1c3f49d`
26a7cd21e2