[FEATURE] Keyboard shortcut to jump between messages in the main interactive view (Ctrl+Up / Ctrl+Down)

Preflight Checklist

• [x] I have searched existing requests and this feature hasn't been requested yet
• [x] This is a single feature request (not multiple features)

Problem Statement

When a conversation gets long, scrolling back to find a previous prompt or a specific Claude reply is slow and imprecise. PgUp/PgDn scrolls by screen, not by message, so I often overshoot or land mid-message. The existing { / } shortcuts only work inside the fullscreen transcript viewer (Ctrl+O), not in the normal interactive view where I'm typing.

Proposed Solution

A pair of keyboard shortcuts — suggestion: Ctrl+Up / Ctrl+Down — that jump the scrollback in the main interactive view directly to the next/previous message boundary (the "white dot" markers). Ideally:

• Ctrl+Up → jump to the previous message (either user prompt or Claude reply, whichever comes next).
• Ctrl+Down → jump to the next message.
• Optional modifier (e.g. Ctrl+Shift+Up/Down) to skip only between Claude replies or only between user prompts.

Alternative Solutions

• { / } in the Ctrl+O transcript view — works, but requires leaving the active prompt and only jumps user prompts.
• v to open the conversation in the editor and search — heavy for quick navigation.
• PgUp/PgDn — by screen, not by message; overshoots constantly.

Priority

Medium - Would be very helpful

Feature Category

Interactive mode (TUI)

Use Case Example

_No response_

Additional Context

This would make long sessions (planning + implementation, debugging loops, code review) much easier to navigate without leaving the interactive view. Bonus: if the shortcuts are configurable in ~/.claude/keybindings.json, users can rebind to their preferred chord.
Related: #40332 (closed as not planned) — this request differs in that it (a) covers both directions of message types, and (b) targets the main interactive view rather than only the fullscreen transcript.