Feature request: Add vim-style j/k navigation for previous message history

Description:
Currently, Claude Code supports Esc + Esc to edit the previous message, but there's no way to navigate through multiple previous messages in the conversation history using vim keys. It would be great to support j (next/down) and k (previous/up) keys for navigating through message history, providing a more seamless vim experience.

Current behavior:

• Esc + Esc edits the previous message only
• Arrow keys work for command history but not message history
• j/k keys work for cursor movement within input

Requested behavior:

• Use j/k to navigate through previous messages in the conversation

Use case:
When you want to edit or resend a message from several exchanges ago, Vim-style navigation would make this much more efficient.