feat(tui): map Ctrl-P/N to arrow navigation in textarea

[aofei]

• Treat Ctrl-P/N (and their C0 fallbacks) the same as Up/Down so cursor movement matches popup/history behavior and control bytes never land in the buffer

Fixes #7529

[github-actions]

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[aofei]

I have read the CLA Document and I hereby sign the CLA

[Copilot]

Pull request overview

This PR adds support for Emacs-style Ctrl-P/N keyboard shortcuts for vertical cursor navigation in the textarea component, matching the behavior already provided for Ctrl-B/F horizontal navigation. The change ensures these control characters are properly mapped to cursor movement rather than being inserted as literal control bytes into the text buffer.

• Maps Ctrl-P to up arrow and Ctrl-N to down arrow for consistent Emacs-style navigation
• Handles both the standard Ctrl+key combinations and C0 control character fallbacks for terminals that don't report the CONTROL modifier

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[etraut-openai]

Thanks for the contribution. The change looks good to me.

One note is that codex is cross-platform, so we need to make sure that key combinations like this work on Windows, which tends to use ctrl key combinations differently than MacOS and Linux.