[BUG] Files open in same panel/sidebar as Claude Code chat instead of main editor

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?

When Claude Code is in the secondary sidebar (right) or bottom panel, clicking any file link opens the file as a tab in the same panel/sidebar area as the chat, instead of the main editor.

What Should Happen?

Files should open in the main editor area (left/center), not alongside the chat window.

Error Messages/Logs

Steps to Reproduce

1. Place Claude Code in the secondary sidebar (right) or bottom panel
2. Click any file link in the chat (or click a file in the Explorer)
3. File opens as a tab next to the Claude Code chat tab, inside the same panel/sidebar
4. Chat window becomes narrow, file preview is very small

Claude Model

None

Is this a regression?

Yes, this worked in a previous version

Last Working Version

_No response_

Claude Code Version

2.1.152

Platform

Other

Operating System

Windows

Terminal/Shell

PowerShell

Additional Information

Root cause investigated in extension.js:
The file is opened using this.panelTab.viewColumn + 1, which resolves to a column inside the secondary sidebar/panel container instead of ViewColumn.One (main editor).