[FEATURE]: Add double-ESC to clear input field

[lifefloating]

Feature hasn't been suggested before.

• [x] I have verified this feature I'm about to request hasn't been suggested before.

Describe the enhancement you want to request

Summary

Add support for double-pressing ESC to clear the input field content.

Motivation

Many popular CLI tools have adopted this pattern:

• Claude Code - support
• Gemini CLI - support
• qwen-code - support

This has become a common UX pattern that users expect in terminal-based AI assistants.