Feature request: /messages - Interactive session history navigation

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

Add a /messages slash command that opens an interactive navigation panel showing the
history of all user prompts in the current session, allowing quick jumping/scrolling to
any specific point in the conversation.

## Motivation

When working on long sessions with many prompts, it becomes difficult to scroll back and
find where a specific change was requested. Currently, the only option is manual
scrolling, which is slow and error-prone.

OpenCode (another CLI coding tool) already implements this as /messages with great
UX:

• Displays a vertical list of all user messages
• Arrow key navigation to highlight a specific message
• Press Enter to auto-scroll/jump to that point in the conversation
• Very useful for locating where a specific change was requested

Proposed Solution

Proposed UX

1. User types /messages
2. An interactive overlay/panel appears (similar to how /help or model selector works)
3. Shows a numbered list of all user prompts with truncated preview
4. User navigates with arrow keys (↑/↓)
5. Enter jumps the viewport to that message
6. Esc closes the panel

Alternative Solutions

_No response_

Priority

Low - Nice to have

Feature Category

Interactive mode (TUI)

Use Case Example

## Example

/messages

Session History (12 messages)
─────────────────────────────

1. Initial project setup with React...
2. Add authentication middleware...
3. Fix the login bug where tokens...

▎ 4. Refactor the database schema to...

1. Add unit tests for the auth module...

...

[↑↓] Navigate [Enter] Jump [Esc] Close

Additional Context

## Prior Art

• OpenCode CLI: implements /messages with this exact behavior
• Neovim Telescope: similar fuzzy-find + jump UX for buffers/history
• Common pattern in TUI applications (fzf, lazygit, etc.)

## Why this matters

Claude Code sessions can get very long (50+ messages). Having a quick way to navigate
the session history would significantly improve the developer experience, especially
when:

• Reviewing what was already done in a session
• Finding where a specific change was requested
• Jumping back to see Claude's response to a particular prompt

## Environment

• Claude Code version: latest
• OS: Windows/macOS/Linux (all platforms would benefit)