[BUG] Shift+Tab not switching to plan mode on Windows

Environment

• Platform (select one):
• [x] Anthropic API
• [ ] AWS Bedrock
• [ ] Google Vertex AI
• [ ] Other: <!-- specify -->
• Claude CLI version: 1.0.51
• Operating System: Windows 11
• Terminal: Powershell 7.5.2

Bug Description

After installing Claude Code on Windows, Shift+Tab fails to switch to plan mode.

Steps to Reproduce

1. run claude in vs code terminal
2. press shift+tab

Expected Behavior

Pressing Shift+Tab should toggle between plan/code modes as documented.

Actual Behavior

Pressing Shift+Tab does nothing - no mode switch occurs, and there's no visual feedback or error message.

Additional Context

None