Document Ctrl+J as alternative for multi-line input

Summary

The documentation for entering multi-line text mentions Escape+Enter and Option+Enter, but these don't work reliably in certain terminal setups.

Problem

When using Claude Code through iTerm2 → SSH → tmux, the standard key combinations for entering newlines (Escape+Enter, Option+Enter) don't work because modifier keys get intercepted by the terminal layers.

Suggestion

Document Ctrl+J as an alternative method for entering newlines. This works at the ASCII level (it's the literal line feed character, code 10) and passes through reliably regardless of terminal configuration.

This would be especially helpful for users running Claude Code:

• Over SSH
• Inside tmux or screen
• In terminal emulators with custom key mappings

Environment

• iTerm2 on macOS connecting via SSH to Linux
• Running inside tmux
• Amazon Linux 2023