## Summary
[@milanglacier reported in
#28653](https://github.com/openai/codex/issues/28653) that the active
mention candidate is hard to distinguish. I suspect [@binbjz’s #28500
report](https://github.com/openai/codex/issues/28500) _(where arrow-key
navigation appeared not to work)_ may describe the same presentation
problem: the selection may have been changing, but the UI was not
showing the active row clearly in their terminal. This PR makes two
small changes to the selection indication behavior:
- Reserve a two-character gutter and mark the active candidate with `> `
for color-agnostic indicator coverage.
- Apply the shared theme-aware accent to the entire selected row for
extra emphasis.
- Update the existing popup snapshot.
Reverse-video styling was considered, but avoided it because it is
overly dependent on the user’s terminal palette.
<img width="2046" height="482" alt="image"
src="https://github.com/user-attachments/assets/b5eb62c3-fd24-4c09-906e-7bd66913b5c6"
/>
## Testing
- `just test -p codex-tui default_unified_mention_popup_snapshot`
- `just clippy -p codex-tui`
- `just fmt`
- Compiled `codex-cli` and tested the unified mentions picker in the
terminal.
canvrno-oai
9bcc09f9f7