Keyboard shortcuts to jump between user messages

[marioaltvater]

Hi! In long Codex conversations, could we have two configurable commands?

• Jump to previous user message
• Jump to next user message

Each press would anchor the nearest user-authored message at the top of the conversation, skipping assistant and tool content. This would make navigation predictable and let Codex Micro or other shortcut devices bind the actions.

Related: #28073 covers a visual prompt navigator; this request is specifically for the keyboard/command counterpart. Thanks!