Feature: navigate/jump to previous user prompts in the current conversation (without terminal scrollback)

Problem

In the default (classic) terminal view there's no quick way to jump back to a message I typed earlier in the current conversation. The only option is scrolling the terminal's native scrollback, which is slow and imprecise in long sessions.

Current state

• Ctrl+O transcript mode (with / search and n/N to move between matches) helps, but only works in fullscreen rendering (/tui fullscreen).
• In the default renderer there's no bindable action or message picker to jump between user prompts, and ~/.claude/keybindings.json doesn't expose a 'previous/next user message' action for the main conversation (the messageSelector:* actions are scoped to the rewind/summarize dialog).

Request

Add a way to navigate between the user's previous prompts in the current conversation without relying on terminal scrollback — for example a message picker (similar to the rewind/summarize selector) or bindable previousUserMessage / nextUserMessage actions — available in the default renderer, not only in fullscreen mode.

Environment

Claude Code in Ghostty on macOS.