TUI startup banner border wraps incorrectly in narrow terminals

What version of Codex CLI is running?

0.144.6 (latest release at the time of filing)

What subscription do you have?

Not provided; this layout issue should be independent of subscription.

Which model were you using?

gpt-5.6-sol, xhigh reasoning

What platform is your computer?

Darwin 25.5.0 arm64 arm

What terminal emulator and version are you using (if applicable)?

Not provided. No terminal multiplexer was reported.

Codex doctor report

Not included because the issue is limited to deterministic startup layout at narrow terminal widths.

What issue are you seeing?

The interactive TUI startup banner is not responsive when the terminal is narrow. The banner is rendered wider than the available viewport, so its horizontal border glyphs overflow and wrap onto additional lines. Content near the right edge, including the model-change hint, also wraps awkwardly outside the intended layout.

What steps can reproduce the bug?

1. Open a terminal and reduce its width to roughly 80 columns, or start wider and resize it until it is narrower than the startup banner.
2. Run codex.
3. Look at the initial OpenAI Codex banner before entering a prompt.
4. Observe that the top and bottom border lines wrap, leaving short detached border segments on following lines.

What is the expected behavior?

The startup banner should clamp its width to the available terminal viewport. Its border should remain intact, and inner content should responsively wrap, truncate, or collapse without drawing beyond the right edge.

Additional information

This reproduces on the current latest release, 0.144.6.

Screenshot evidence

<img width="433" height="394" alt="Image" src="https://github.com/user-attachments/assets/2e1ff4fe-2860-4abd-b7fd-1451d713a1c5" />