[BUG] vscode plan mode only works via button clicking, not slash command

Preflight Checklist

• [x] I have searched existing issues and this hasn't been reported yet
• [x] This is a single bug report (please file separate reports for different bugs)
• [x] I am using the latest version of Claude Code

What's Wrong?

<img width="189" height="243" alt="Image" src="https://github.com/user-attachments/assets/e66bf8c5-cac5-4de9-bee6-019cae4c0078" />
as you can see from the screenshot, in official claude code vscode plugin, I can enter plan mode by clicking on the button below the chat box, but slash command /plan does not exist

What Should Happen?

/plan command should exist and allow autocomplete

Error Messages/Logs

Steps to Reproduce

Use vscode claude code plugin and type /plan

Claude Model

Sonnet (default)

Is this a regression?

Yes, this worked in a previous version

Last Working Version

_No response_

Claude Code Version

2.1.70

Platform

Anthropic API

Operating System

Windows

Terminal/Shell

VS Code integrated terminal

Additional Information

_No response_