Caps Lock key prints raw escape sequence [57358u in terminal

Bug Description

When pressing Caps Lock while using Claude Code in VS Code's integrated terminal, the raw Kitty keyboard protocol escape sequence [57358u is printed as visible text in the chat input.

57358 is the Kitty keyboard protocol keycode for Caps Lock. The sequence is being passed through to the input instead of being silently consumed.

Expected Behavior

Modifier-only key events from the Kitty keyboard protocol (Caps Lock, Shift, Ctrl, Alt, etc.) should be silently ignored and not rendered as text.

Steps to Reproduce

1. Open Claude Code in VS Code's integrated terminal (Linux)
2. Press Caps Lock while in the chat input
3. [57358u appears as typed text

Environment

• OS: Linux (Ubuntu)
• Terminal: VS Code integrated terminal
• TERM: xterm-256color
• Shell: bash