Add option to disable mouse tracking in TUI

Problem

When running Claude Code inside a terminal multiplexer (e.g., zellij) that has its own mouse mode enabled, clicking inside the Claude Code pane generates garbage characters like [M, [<0;45;12M, etc. This happens because both Claude Code (via Ink/React) and the multiplexer enable mouse tracking escape sequences (\e[?1000h, \e[?1003h, \e[?1006h), and the two layers conflict.

This does not happen in a plain terminal without a multiplexer.

Environment

• Windows Terminal → SSH → Ubuntu 24.04 → zellij → Claude Code
• zellij with mouse_mode true (the default)
• The issue likely affects tmux with set -g mouse on as well

Current workarounds

• Disable mouse mode in the multiplexer (loses multiplexer mouse features)
• Run Claude Code outside the multiplexer (loses session persistence)
• Avoid clicking inside the Claude Code pane (not always practical)

Requested feature

A config option or CLI flag (e.g., --no-mouse or "mouse": false in settings) to disable mouse tracking in Claude Code's TUI. This would let the terminal multiplexer handle mouse events without conflict, while Claude Code remains fully functional via keyboard.

Claude Code is entirely keyboard-driven, so disabling mouse tracking should have no functional impact.