Support mouse click-to-position cursor in the input editor

Feature Request

Is your feature request related to a problem?
When editing long prompts in Claude Code's TUI input field, there's no way to click with the mouse to position the cursor at a specific point in the text. Users must rely on keyboard shortcuts (Ctrl+A/E, Option+Arrow, arrow keys) to navigate, which is slow for long inputs.

Describe the solution you'd like
Support mouse click-to-position in the input editor, so clicking at a point in the text moves the cursor there — similar to how Warp's input editor or any standard text field works.

Describe alternatives you've considered

• Using terminal emulators with click-to-position (Warp, iTerm2) — but these can't override Claude Code's custom TUI input handling
• Keyboard navigation (Ctrl+A/E, Option+Arrow) — functional but slower than clicking

Additional context
Modern terminal emulators support mouse reporting, and many TUI frameworks (e.g., Ink, which Claude Code uses) can consume mouse events. This would be a quality-of-life improvement for anyone editing multi-line or long prompts.